From: Andreas Schwab Date: Wed, 19 Feb 2020 16:21:46 +0000 (+0100) Subject: Fix use-after-free in glob when expanding ~user (bug 25414) X-Git-Url: https://sourceware.org/git/?p=glibc.git;a=commitdiff_plain;h=da97c6b88eb03fb834e92964b0895c2ac8d61f63;hp=dd34bce38c822b67fcc42e73969bf6699d6874b6 Fix use-after-free in glob when expanding ~user (bug 25414) 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 ddc650e9b3dc916eab417ce9f79e67337b05035c) --- diff --git a/posix/glob.c b/posix/glob.c index e73e35c510..c6cbd0eb43 100644 --- a/posix/glob.c +++ b/posix/glob.c @@ -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; }