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| author | Zizhi Wo <wozizhi@huawei.com> | 2024-11-07 14:06:48 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-11-11 16:39:38 +0300 |
| commit | 31ad74b20227ce6b40910ff78b1c604e42975cf1 (patch) | |
| tree | 36aab27035108a3eedddf92c30ce91a7e1674d00 /fs/cachefiles/interface.c | |
| parent | 09ecf8f5505465b5527a39dff4b159af62306eee (diff) | |
| download | linux-31ad74b20227ce6b40910ff78b1c604e42975cf1.tar.xz | |
cachefiles: Fix NULL pointer dereference in object->file
At present, the object->file has the NULL pointer dereference problem in
ondemand-mode. The root cause is that the allocated fd and object->file
lifetime are inconsistent, and the user-space invocation to anon_fd uses
object->file. Following is the process that triggers the issue:
[write fd] [umount]
cachefiles_ondemand_fd_write_iter
fscache_cookie_state_machine
cachefiles_withdraw_cookie
if (!file) return -ENOBUFS
cachefiles_clean_up_object
cachefiles_unmark_inode_in_use
fput(object->file)
object->file = NULL
// file NULL pointer dereference!
__cachefiles_write(..., file, ...)
Fix this issue by add an additional reference count to the object->file
before write/llseek, and decrement after it finished.
Fixes: c8383054506c ("cachefiles: notify the user daemon when looking up cookie")
Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
Link: https://lore.kernel.org/r/20241107110649.3980193-5-wozizhi@huawei.com
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/cachefiles/interface.c')
| -rw-r--r-- | fs/cachefiles/interface.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c index 35ba2117a6f6..3e63cfe15874 100644 --- a/fs/cachefiles/interface.c +++ b/fs/cachefiles/interface.c @@ -327,6 +327,8 @@ static void cachefiles_commit_object(struct cachefiles_object *object, static void cachefiles_clean_up_object(struct cachefiles_object *object, struct cachefiles_cache *cache) { + struct file *file; + if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) { if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) { cachefiles_see_object(object, cachefiles_obj_see_clean_delete); @@ -342,10 +344,14 @@ static void cachefiles_clean_up_object(struct cachefiles_object *object, } cachefiles_unmark_inode_in_use(object, object->file); - if (object->file) { - fput(object->file); - object->file = NULL; - } + + spin_lock(&object->lock); + file = object->file; + object->file = NULL; + spin_unlock(&object->lock); + + if (file) + fput(file); } /* |