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socket: Check lengths before advancing pointer in CMSG_NXTHDR
The inline and library functions that the CMSG_NXTHDR macro may expand to increment the pointer to the header before checking the stride of the increment against available space. Since C only allows incrementing pointers to one past the end of an array, the increment must be done after a length check. This commit fixes that and includes a regression test for CMSG_FIRSTHDR and CMSG_NXTHDR. The Linux, Hurd, and generic headers are all changed. Tested on Linux on armv7hl, i686, x86_64, aarch64, ppc64le, and s390x. [BZ #28846] Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
parent
521d540562
commit
9c443ac455
@ -245,6 +245,12 @@ struct cmsghdr
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+ CMSG_ALIGN (sizeof (struct cmsghdr)))
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#define CMSG_LEN(len) (CMSG_ALIGN (sizeof (struct cmsghdr)) + (len))
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/* Given a length, return the additional padding necessary such that
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len + __CMSG_PADDING(len) == CMSG_ALIGN (len). */
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#define __CMSG_PADDING(len) ((sizeof (size_t) \
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- ((len) & (sizeof (size_t) - 1))) \
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& (sizeof (size_t) - 1))
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extern struct cmsghdr *__cmsg_nxthdr (struct msghdr *__mhdr,
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struct cmsghdr *__cmsg) __THROW;
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#ifdef __USE_EXTERN_INLINES
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@ -254,18 +260,38 @@ extern struct cmsghdr *__cmsg_nxthdr (struct msghdr *__mhdr,
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_EXTERN_INLINE struct cmsghdr *
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__NTH (__cmsg_nxthdr (struct msghdr *__mhdr, struct cmsghdr *__cmsg))
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{
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/* We may safely assume that __cmsg lies between __mhdr->msg_control and
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__mhdr->msg_controllen because the user is required to obtain the first
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cmsg via CMSG_FIRSTHDR, set its length, then obtain subsequent cmsgs
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via CMSG_NXTHDR, setting lengths along the way. However, we don't yet
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trust the value of __cmsg->cmsg_len and therefore do not use it in any
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pointer arithmetic until we check its value. */
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unsigned char * __msg_control_ptr = (unsigned char *) __mhdr->msg_control;
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unsigned char * __cmsg_ptr = (unsigned char *) __cmsg;
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size_t __size_needed = sizeof (struct cmsghdr)
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+ __CMSG_PADDING (__cmsg->cmsg_len);
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/* The current header is malformed, too small to be a full header. */
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if ((size_t) __cmsg->cmsg_len < sizeof (struct cmsghdr))
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/* The kernel header does this so there may be a reason. */
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return (struct cmsghdr *) 0;
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/* There isn't enough space between __cmsg and the end of the buffer to
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hold the current cmsg *and* the next one. */
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if (((size_t)
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(__msg_control_ptr + __mhdr->msg_controllen - __cmsg_ptr)
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< __size_needed)
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|| ((size_t)
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(__msg_control_ptr + __mhdr->msg_controllen - __cmsg_ptr
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- __size_needed)
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< __cmsg->cmsg_len))
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return (struct cmsghdr *) 0;
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/* Now, we trust cmsg_len and can use it to find the next header. */
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__cmsg = (struct cmsghdr *) ((unsigned char *) __cmsg
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+ CMSG_ALIGN (__cmsg->cmsg_len));
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if ((unsigned char *) (__cmsg + 1) > ((unsigned char *) __mhdr->msg_control
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+ __mhdr->msg_controllen)
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|| ((unsigned char *) __cmsg + CMSG_ALIGN (__cmsg->cmsg_len)
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> ((unsigned char *) __mhdr->msg_control + __mhdr->msg_controllen)))
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/* No more entries. */
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return (struct cmsghdr *) 0;
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return __cmsg;
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}
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#endif /* Use `extern inline'. */
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@ -34,6 +34,7 @@ routines := accept bind connect getpeername getsockname getsockopt \
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tests := \
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tst-accept4 \
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tst-sockopt \
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tst-cmsghdr \
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# tests
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tests-internal := \
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92
socket/tst-cmsghdr-skeleton.c
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92
socket/tst-cmsghdr-skeleton.c
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@ -0,0 +1,92 @@
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/* Test ancillary data header creation.
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Copyright (C) 2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* We use the preprocessor to generate the function/macro tests instead of
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using indirection because having all the macro expansions alongside
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each other lets the compiler warn us about suspicious pointer
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arithmetic across subsequent CMSG_{FIRST,NXT}HDR expansions. */
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#include <stdint.h>
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#define RUN_TEST_CONCAT(suffix) run_test_##suffix
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#define RUN_TEST_FUNCNAME(suffix) RUN_TEST_CONCAT (suffix)
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static void
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RUN_TEST_FUNCNAME (CMSG_NXTHDR_IMPL) (void)
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{
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struct msghdr m = {0};
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struct cmsghdr *cmsg;
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char cmsgbuf[3 * CMSG_SPACE (sizeof (PAYLOAD))] = {0};
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m.msg_control = cmsgbuf;
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m.msg_controllen = sizeof (cmsgbuf);
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/* First header should point to the start of the buffer. */
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cmsg = CMSG_FIRSTHDR (&m);
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TEST_VERIFY_EXIT ((char *) cmsg == cmsgbuf);
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/* If the first header length consumes the entire buffer, there is no
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space remaining for additional headers. */
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cmsg->cmsg_len = sizeof (cmsgbuf);
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg == NULL);
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/* The first header length is so big, using it would cause an overflow. */
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cmsg = CMSG_FIRSTHDR (&m);
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TEST_VERIFY_EXIT ((char *) cmsg == cmsgbuf);
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cmsg->cmsg_len = SIZE_MAX;
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg == NULL);
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/* The first header leaves just enough space to hold another header. */
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cmsg = CMSG_FIRSTHDR (&m);
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TEST_VERIFY_EXIT ((char *) cmsg == cmsgbuf);
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cmsg->cmsg_len = sizeof (cmsgbuf) - sizeof (struct cmsghdr);
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg != NULL);
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/* The first header leaves space but not enough for another header. */
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cmsg = CMSG_FIRSTHDR (&m);
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TEST_VERIFY_EXIT ((char *) cmsg == cmsgbuf);
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cmsg->cmsg_len ++;
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg == NULL);
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/* The second header leaves just enough space to hold another header. */
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cmsg = CMSG_FIRSTHDR (&m);
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TEST_VERIFY_EXIT ((char *) cmsg == cmsgbuf);
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cmsg->cmsg_len = CMSG_LEN (sizeof (PAYLOAD));
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg != NULL);
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cmsg->cmsg_len = sizeof (cmsgbuf)
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- CMSG_SPACE (sizeof (PAYLOAD)) /* First header. */
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- sizeof (struct cmsghdr);
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg != NULL);
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/* The second header leaves space but not enough for another header. */
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cmsg = CMSG_FIRSTHDR (&m);
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TEST_VERIFY_EXIT ((char *) cmsg == cmsgbuf);
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg != NULL);
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cmsg->cmsg_len ++;
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cmsg = CMSG_NXTHDR_IMPL (&m, cmsg);
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TEST_VERIFY_EXIT (cmsg == NULL);
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return;
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}
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56
socket/tst-cmsghdr.c
Normal file
56
socket/tst-cmsghdr.c
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@ -0,0 +1,56 @@
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/* Test ancillary data header creation.
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Copyright (C) 2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sys/socket.h>
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#include <gnu/lib-names.h>
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#include <support/xdlfcn.h>
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#include <support/check.h>
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#define PAYLOAD "Hello, World!"
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/* CMSG_NXTHDR is a macro that calls an inline function defined in
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bits/socket.h. In case the function cannot be inlined, libc.so carries
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a copy. Both versions need to be tested. */
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#define CMSG_NXTHDR_IMPL CMSG_NXTHDR
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#include "tst-cmsghdr-skeleton.c"
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#undef CMSG_NXTHDR_IMPL
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static struct cmsghdr * (* cmsg_nxthdr) (struct msghdr *, struct cmsghdr *);
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#define CMSG_NXTHDR_IMPL cmsg_nxthdr
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#include "tst-cmsghdr-skeleton.c"
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#undef CMSG_NXTHDR_IMPL
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static int
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do_test (void)
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{
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static void *handle;
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run_test_CMSG_NXTHDR ();
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handle = xdlopen (LIBC_SO, RTLD_LAZY);
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cmsg_nxthdr = (struct cmsghdr * (*) (struct msghdr *, struct cmsghdr *))
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xdlsym (handle, "__cmsg_nxthdr");
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run_test_cmsg_nxthdr ();
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return 0;
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}
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#include <support/test-driver.c>
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@ -249,6 +249,12 @@ struct cmsghdr
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+ CMSG_ALIGN (sizeof (struct cmsghdr)))
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#define CMSG_LEN(len) (CMSG_ALIGN (sizeof (struct cmsghdr)) + (len))
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/* Given a length, return the additional padding necessary such that
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len + __CMSG_PADDING(len) == CMSG_ALIGN (len). */
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#define __CMSG_PADDING(len) ((sizeof (size_t) \
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- ((len) & (sizeof (size_t) - 1))) \
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& (sizeof (size_t) - 1))
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extern struct cmsghdr *__cmsg_nxthdr (struct msghdr *__mhdr,
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struct cmsghdr *__cmsg) __THROW;
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#ifdef __USE_EXTERN_INLINES
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@ -258,18 +264,38 @@ extern struct cmsghdr *__cmsg_nxthdr (struct msghdr *__mhdr,
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_EXTERN_INLINE struct cmsghdr *
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__NTH (__cmsg_nxthdr (struct msghdr *__mhdr, struct cmsghdr *__cmsg))
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{
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/* We may safely assume that __cmsg lies between __mhdr->msg_control and
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__mhdr->msg_controllen because the user is required to obtain the first
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cmsg via CMSG_FIRSTHDR, set its length, then obtain subsequent cmsgs
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via CMSG_NXTHDR, setting lengths along the way. However, we don't yet
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trust the value of __cmsg->cmsg_len and therefore do not use it in any
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pointer arithmetic until we check its value. */
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unsigned char * __msg_control_ptr = (unsigned char *) __mhdr->msg_control;
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unsigned char * __cmsg_ptr = (unsigned char *) __cmsg;
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size_t __size_needed = sizeof (struct cmsghdr)
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+ __CMSG_PADDING (__cmsg->cmsg_len);
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/* The current header is malformed, too small to be a full header. */
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if ((size_t) __cmsg->cmsg_len < sizeof (struct cmsghdr))
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/* The kernel header does this so there may be a reason. */
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return (struct cmsghdr *) 0;
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/* There isn't enough space between __cmsg and the end of the buffer to
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hold the current cmsg *and* the next one. */
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if (((size_t)
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(__msg_control_ptr + __mhdr->msg_controllen - __cmsg_ptr)
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< __size_needed)
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|| ((size_t)
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(__msg_control_ptr + __mhdr->msg_controllen - __cmsg_ptr
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- __size_needed)
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< __cmsg->cmsg_len))
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return (struct cmsghdr *) 0;
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/* Now, we trust cmsg_len and can use it to find the next header. */
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__cmsg = (struct cmsghdr *) ((unsigned char *) __cmsg
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+ CMSG_ALIGN (__cmsg->cmsg_len));
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if ((unsigned char *) (__cmsg + 1) > ((unsigned char *) __mhdr->msg_control
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+ __mhdr->msg_controllen)
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|| ((unsigned char *) __cmsg + CMSG_ALIGN (__cmsg->cmsg_len)
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> ((unsigned char *) __mhdr->msg_control + __mhdr->msg_controllen)))
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/* No more entries. */
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return (struct cmsghdr *) 0;
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return __cmsg;
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}
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#endif /* Use `extern inline'. */
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@ -307,6 +307,12 @@ struct cmsghdr
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+ CMSG_ALIGN (sizeof (struct cmsghdr)))
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#define CMSG_LEN(len) (CMSG_ALIGN (sizeof (struct cmsghdr)) + (len))
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/* Given a length, return the additional padding necessary such that
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len + __CMSG_PADDING(len) == CMSG_ALIGN (len). */
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#define __CMSG_PADDING(len) ((sizeof (size_t) \
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- ((len) & (sizeof (size_t) - 1))) \
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& (sizeof (size_t) - 1))
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extern struct cmsghdr *__cmsg_nxthdr (struct msghdr *__mhdr,
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struct cmsghdr *__cmsg) __THROW;
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#ifdef __USE_EXTERN_INLINES
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@ -316,18 +322,38 @@ extern struct cmsghdr *__cmsg_nxthdr (struct msghdr *__mhdr,
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_EXTERN_INLINE struct cmsghdr *
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__NTH (__cmsg_nxthdr (struct msghdr *__mhdr, struct cmsghdr *__cmsg))
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{
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/* We may safely assume that __cmsg lies between __mhdr->msg_control and
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__mhdr->msg_controllen because the user is required to obtain the first
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cmsg via CMSG_FIRSTHDR, set its length, then obtain subsequent cmsgs
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via CMSG_NXTHDR, setting lengths along the way. However, we don't yet
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trust the value of __cmsg->cmsg_len and therefore do not use it in any
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pointer arithmetic until we check its value. */
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unsigned char * __msg_control_ptr = (unsigned char *) __mhdr->msg_control;
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unsigned char * __cmsg_ptr = (unsigned char *) __cmsg;
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size_t __size_needed = sizeof (struct cmsghdr)
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+ __CMSG_PADDING (__cmsg->cmsg_len);
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/* The current header is malformed, too small to be a full header. */
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if ((size_t) __cmsg->cmsg_len < sizeof (struct cmsghdr))
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/* The kernel header does this so there may be a reason. */
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return (struct cmsghdr *) 0;
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/* There isn't enough space between __cmsg and the end of the buffer to
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hold the current cmsg *and* the next one. */
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if (((size_t)
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(__msg_control_ptr + __mhdr->msg_controllen - __cmsg_ptr)
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< __size_needed)
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|| ((size_t)
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(__msg_control_ptr + __mhdr->msg_controllen - __cmsg_ptr
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- __size_needed)
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< __cmsg->cmsg_len))
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return (struct cmsghdr *) 0;
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/* Now, we trust cmsg_len and can use it to find the next header. */
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__cmsg = (struct cmsghdr *) ((unsigned char *) __cmsg
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+ CMSG_ALIGN (__cmsg->cmsg_len));
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if ((unsigned char *) (__cmsg + 1) > ((unsigned char *) __mhdr->msg_control
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+ __mhdr->msg_controllen)
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|| ((unsigned char *) __cmsg + CMSG_ALIGN (__cmsg->cmsg_len)
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> ((unsigned char *) __mhdr->msg_control + __mhdr->msg_controllen)))
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/* No more entries. */
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return (struct cmsghdr *) 0;
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return __cmsg;
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}
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#endif /* Use `extern inline'. */
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@ -23,18 +23,38 @@
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struct cmsghdr *
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__cmsg_nxthdr (struct msghdr *mhdr, struct cmsghdr *cmsg)
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{
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if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
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/* The kernel header does this so there may be a reason. */
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return NULL;
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/* We may safely assume that cmsg lies between mhdr->msg_control and
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mhdr->msg_controllen because the user is required to obtain the first
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cmsg via CMSG_FIRSTHDR, set its length, then obtain subsequent cmsgs
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via CMSG_NXTHDR, setting lengths along the way. However, we don't yet
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trust the value of cmsg->cmsg_len and therefore do not use it in any
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pointer arithmetic until we check its value. */
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unsigned char * msg_control_ptr = (unsigned char *) mhdr->msg_control;
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unsigned char * cmsg_ptr = (unsigned char *) cmsg;
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size_t size_needed = sizeof (struct cmsghdr)
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+ __CMSG_PADDING (cmsg->cmsg_len);
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/* The current header is malformed, too small to be a full header. */
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if ((size_t) cmsg->cmsg_len < sizeof (struct cmsghdr))
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return (struct cmsghdr *) 0;
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/* There isn't enough space between cmsg and the end of the buffer to
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hold the current cmsg *and* the next one. */
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if (((size_t)
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(msg_control_ptr + mhdr->msg_controllen - cmsg_ptr)
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< size_needed)
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|| ((size_t)
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(msg_control_ptr + mhdr->msg_controllen - cmsg_ptr
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- size_needed)
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< cmsg->cmsg_len))
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return (struct cmsghdr *) 0;
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/* Now, we trust cmsg_len and can use it to find the next header. */
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cmsg = (struct cmsghdr *) ((unsigned char *) cmsg
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+ CMSG_ALIGN (cmsg->cmsg_len));
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if ((unsigned char *) (cmsg + 1) > ((unsigned char *) mhdr->msg_control
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+ mhdr->msg_controllen)
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|| ((unsigned char *) cmsg + CMSG_ALIGN (cmsg->cmsg_len)
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> ((unsigned char *) mhdr->msg_control + mhdr->msg_controllen)))
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/* No more entries. */
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return NULL;
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return cmsg;
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}
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libc_hidden_def (__cmsg_nxthdr)
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