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Fix use-after-free in glob when expanding ~user (bug 25414)

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The value of `end_name' points into the value of `dirname', thus don't
deallocate the latter before the last use of the former.

(cherry picked from commit ddc650e9b3)
This commit is contained in:
Andreas Schwab 2020-02-19 17:21:46 +01:00 committed by Tulio Magno Quites Machado Filho
parent 0478174d1e
commit 21344a3d62
2 changed files with 17 additions and 12 deletions
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4
NEWS
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@ -73,6 +73,7 @@ The following bugs are resolved with this release:
[25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs
[25225] ld.so fails to link on x86 if GCC defaults to -fcf-protection
[25232] No const correctness for strchr et al. for Clang++
[25414] 'glob' use-after-free bug (CVE-2020-1752)
[25423] Array overflow in backtrace on powerpc
Security related changes:
@ -109,6 +110,9 @@ Security related changes:
addresses for loaded libraries and thus bypass ASLR for a setuid
program. Reported by Marcin Kościelnicki.
CVE-2020-1752: A use-after-free vulnerability in the glob function when
expanding ~user has been fixed.
Version 2.28

25
posix/glob.c
View File

@ -827,31 +827,32 @@ __glob (const char *pattern, int flags, int (*errfunc) (const char *, int),
{
size_t home_len = strlen (p->pw_dir);
size_t rest_len = end_name == NULL ? 0 : strlen (end_name);
char *d;
char *d, *newp;
bool use_alloca = glob_use_alloca (alloca_used,
home_len + rest_len + 1);
if (__glibc_unlikely (malloc_dirname))
free (dirname);
malloc_dirname = 0;
if (glob_use_alloca (alloca_used, home_len + rest_len + 1))
dirname = alloca_account (home_len + rest_len + 1,
alloca_used);
if (use_alloca)
newp = alloca_account (home_len + rest_len + 1, alloca_used);
else
{
dirname = malloc (home_len + rest_len + 1);
if (dirname == NULL)
newp = malloc (home_len + rest_len + 1);
if (newp == NULL)
{
scratch_buffer_free (&pwtmpbuf);
retval = GLOB_NOSPACE;
goto out;
}
malloc_dirname = 1;
}
d = mempcpy (dirname, p->pw_dir, home_len);
d = mempcpy (newp, p->pw_dir, home_len);
if (end_name != NULL)
d = mempcpy (d, end_name, rest_len);
*d = '\0';
if (__glibc_unlikely (malloc_dirname))
free (dirname);
dirname = newp;
malloc_dirname = !use_alloca;
dirlen = home_len + rest_len;
dirname_modified = 1;
}