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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 with
 changes from commit d711a00f93)
This commit is contained in:
Andreas Schwab 2020-02-19 17:21:46 +01:00 committed by Tulio Magno Quites Machado Filho
parent 37db4539dd
commit 263e617599
2 changed files with 21 additions and 11 deletions
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4
NEWS
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@ -394,6 +394,9 @@ Security related changes:
* A use-after-free vulnerability in clntudp_call in the Sun RPC system has been
fixed (CVE-2017-12133).
* A use-after-free vulnerability in the glob function when expanding ~user has
been fixed (CVE-2020-1752).
The following bugs are resolved with this release:
[984] network: Respond to changed resolv.conf in gethostbyname
@ -621,6 +624,7 @@ The following bugs are resolved with this release:
[21839] localedata: Fix LC_MONETARY for ta_LK
[21844] localedata: Fix Latin characters and Months Sequence.
[21848] localedata: Fix mai_NP Title Name
[25414] 'glob' use-after-free bug (CVE-2020-1752)
Version 2.25

28
posix/glob.c
View File

@ -947,26 +947,32 @@ 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);
if (__glibc_unlikely (malloc_dirname))
free (dirname);
malloc_dirname = 0;
char *d, *newp;
bool use_alloca = glob_use_alloca (alloca_used,
home_len + rest_len + 1);
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)
{
free (malloc_pwtmpbuf);
retval = GLOB_NOSPACE;
goto out;
}
malloc_dirname = 1;
}
*((char *) mempcpy (mempcpy (dirname, p->pw_dir, home_len),
end_name, rest_len)) = '\0';
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;