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powerpc: Use correct procedure call standard for getrandom vDSO call (bug 32440)

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A plain indirect function call does not work on POWER because
success and failure are signaled through a flag register, and
not via the usual Linux negative return value convention.

This has potential security impact, in two ways: the return value
could be out of bounds (EAGAIN is 11 on powerpc6le), and no
random bytes have been written despite the non-error return value.

Fixes commit 461cab1de7 ("linux: Add
support for getrandom vDSO").

Reported-by: Ján Stanček <jstancek@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Florian Weimer 2024-12-10 16:17:06 +01:00
parent b79f257533
commit 4f5704ea34
3 changed files with 49 additions and 6 deletions
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1
stdlib/Makefile
View File

@ -281,6 +281,7 @@ tests := \
tst-getenv-thread \
tst-getenv-unsetenv \
tst-getrandom \
tst-getrandom-errno \
tst-getrandom2 \
tst-labs \
tst-limits \

37
stdlib/tst-getrandom-errno.c Normal file
View File

@ -0,0 +1,37 @@
/* Test errno handling in getrandom (bug 32440).
Copyright (C) 2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <stdlib.h>
#include <support/check.h>
#include <sys/random.h>
static
int do_test (void)
{
errno = -1181968554; /* Just a random value. */
char buf[4];
int ret = getrandom (buf, sizeof (buf), -1); /* All flags set. */
if (errno != ENOSYS)
TEST_COMPARE (errno, EINVAL);
TEST_COMPARE (ret, -1);
return 0;
}
#include <support/test-driver.c>

17
sysdeps/unix/sysv/linux/getrandom.c
View File

@ -20,6 +20,8 @@
#include <errno.h>
#include <unistd.h>
#include <sysdep-cancel.h>
#include <sysdep.h>
#include <sysdep-vdso.h>
static inline ssize_t
getrandom_syscall (void *buffer, size_t length, unsigned int flags,
@ -201,11 +203,12 @@ getrandom_vdso (void *buffer, size_t length, unsigned int flags, bool cancel)
cancellation bridge (__syscall_cancel_arch), use GRND_NONBLOCK so there
is no potential unbounded blocking in the kernel. It should be a rare
situation, only at system startup when RNG is not initialized. */
ssize_t ret = GLRO (dl_vdso_getrandom) (buffer,
length,
flags | GRND_NONBLOCK,
state,
state_size);
long int ret = INTERNAL_VSYSCALL_CALL (GLRO (dl_vdso_getrandom), 5,
buffer,
length,
flags | GRND_NONBLOCK,
state,
state_size);
if (INTERNAL_SYSCALL_ERROR_P (ret))
{
/* Fallback to the syscall if the kernel would block. */
@ -241,7 +244,9 @@ __getrandom_early_init (_Bool initial)
uint32_t mmap_flags;
uint32_t reserved[13];
} params;
if (GLRO(dl_vdso_getrandom) (NULL, 0, 0, &params, ~0UL) == 0)
long int ret = INTERNAL_VSYSCALL_CALL (GLRO(dl_vdso_getrandom),
5, NULL, 0, 0, &params, ~0UL);
if (! INTERNAL_SYSCALL_ERROR_P (ret))
{
/* Align each opaque state to L1 data cache size to avoid false
sharing. If the size can not be obtained, use the kernel