2019-07-23 23:08:36

by Jia-Ju Bai

Subject: [PATCH] fs: afs: Fix a possible null-pointer dereference in afs_put_read()

In afs_read_dir(), there is an if statement on line 255 to check whether
req->pages is NULL:
if (!req->pages)
goto error;

If req->pages is NULL, afs_put_read() on line 337 is executed.
In afs_put_read(), req->pages[i] is used on line 195.
Thus, a possible null-pointer dereference may occur in this case.

To fix this possible bug, an if statement is added in afs_put_read() to
check req->pages.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
fs/afs/file.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 56b69576274d..dd3c55c9101c 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -191,11 +191,13 @@ void afs_put_read(struct afs_read *req)
int i;

if (refcount_dec_and_test(&req->usage)) {
- for (i = 0; i < req->nr_pages; i++)
- if (req->pages[i])
- put_page(req->pages[i]);
- if (req->pages != req->array)
- kfree(req->pages);
+ if (req->pages) {
+ for (i = 0; i < req->nr_pages; i++)
+ if (req->pages[i])
+ put_page(req->pages[i]);
+ if (req->pages != req->array)
+ kfree(req->pages);
+ }
kfree(req);
}
}
--
2.17.0

2019-07-30 16:40:46

by David Howells

Subject: Re: [PATCH] fs: afs: Fix a possible null-pointer dereference in afs_put_read()

This is in my afs-fixes branch.

David