Re: [PATCH] fs: ext4: Fix dereferencing the null pointer 'ptr'

[Stefan Roese]

On 23.11.22 09:06, Mikhail Ilin wrote:

  If memory allocation fails on line 780, then 'fail' will be
  jumped to and 'ptr' will be null, causing it to be dereferenced it on line
  855. Thus, before using 'ptr[i]' one must make sure that the 'ptr' pointer
  is not NULL.

Nitpicking. You seem to have a leading space in this comment
block. Please remove next time.

Fixes: 934b14f2bb30 ("ext4: free allocations by parse_path()")
Signed-off-by: Mikhail Ilin <ilin.mikhail...@gmail.com>
---
  fs/ext4/ext4_common.c | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 1185cb2c04..3cdd1a04a9 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -851,10 +851,12 @@ end:
  fail:
        free(depth_dirname);
        free(parse_dirname);
-       for (i = 0; i < depth; i++) {
-               if (!ptr[i])
-                       break;
-               free(ptr[i]);
+       if (ptr) {
+               for (i = 0; i < depth; i++) {
+                       if (!ptr[i])
+                               break;
+                       free(ptr[i]);
+               }
        }
        free(ptr);

Won't this fail with ptr == NULL? Please also include the free(ptr) into
the if (ptr) { } part.

Thanks,
Stefan