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realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
realpath returns an allocated string when the result exceeds PATH_MAX, which is unexpected when its second argument is not NULL. This results in the second argument (resolved) being uninitialized and also results in a memory leak since the caller expects resolved to be the same as the returned value. Return NULL and set errno to ENAMETOOLONG if the result exceeds PATH_MAX. This fixes [BZ #28770], which is CVE-2021-3998. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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@ -166,6 +166,10 @@ Security related changes:
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CVE-2022-23218: Passing an overlong file name to the svcunix_create
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legacy function could result in a stack-based buffer overflow.
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CVE-2021-3998: Passing a path longer than PATH_MAX to the realpath
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function could result in a memory leak and potential access of
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uninitialized memory. Reported by Qualys.
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The following bugs are resolved with this release:
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[The release manager will add the list generated by
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@ -109,6 +109,7 @@ tests := \
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tst-random \
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tst-random2 \
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tst-realpath \
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tst-realpath-toolong \
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tst-secure-getenv \
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tst-setcontext \
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tst-setcontext2 \
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@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved,
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error:
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*dest++ = '\0';
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if (resolved != NULL && dest - rname <= get_path_max ())
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rname = strcpy (resolved, rname);
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if (resolved != NULL)
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{
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if (dest - rname <= get_path_max ())
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rname = strcpy (resolved, rname);
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else
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{
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failed = true;
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__set_errno (ENAMETOOLONG);
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}
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}
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error_nomem:
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scratch_buffer_free (&extra_buffer);
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49
stdlib/tst-realpath-toolong.c
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49
stdlib/tst-realpath-toolong.c
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@ -0,0 +1,49 @@
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/* Verify that realpath returns NULL with ENAMETOOLONG if the result exceeds
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NAME_MAX.
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Copyright The GNU Toolchain Authors.
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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 <errno.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <support/check.h>
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#include <support/temp_file.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#define BASENAME "tst-realpath-toolong."
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int
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do_test (void)
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{
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char *base = support_create_and_chdir_toolong_temp_directory (BASENAME);
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char buf[PATH_MAX + 1];
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const char *res = realpath (".", buf);
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/* canonicalize.c states that if the real path is >= PATH_MAX, then
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realpath returns NULL and sets ENAMETOOLONG. */
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TEST_VERIFY (res == NULL);
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TEST_VERIFY (errno == ENAMETOOLONG);
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free (base);
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return 0;
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}
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#include <support/test-driver.c>
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