Fix use-after-free in glob when expanding ~user (bug 25414)
Commit Message
The value of `end_name' points into the value of `dirname', thus don't
deallocate the latter before the last use of the former.
---
posix/glob.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
Comments
On 2/19/20 8:50 AM, Andreas Schwab wrote:
> + int use_alloca = glob_use_alloca (alloca_used,
> + home_len + rest_len + 1);
I suggest using 'bool' instead of 'int' here, since the value is boolean
and glob_use_alloca returns 'bool'. Although some of the nearby local
vars use 'int' to represent booleans, surely this is because the code
predates 'bool'; for new code it's better to use 'bool' for booleans.
Otherwise, looks good; thanks.
@@ -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;
+ int 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;
}