* [PATCH] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks
@ 2019-11-28 0:18 Pavel Shilovsky
2019-12-01 5:27 ` Steve French
2019-12-02 12:25 ` Aurélien Aptel
0 siblings, 2 replies; 3+ messages in thread
From: Pavel Shilovsky @ 2019-11-28 0:18 UTC (permalink / raw)
To: Steve French, linux-cifs; +Cc: Long Li
Currently when the client creates a cifsFileInfo structure for
a newly opened file, it allocates a list of byte-range locks
with a pointer to the new cfile and attaches this list to the
inode's lock list. The latter happens before initializing all
other fields, e.g. cfile->tlink. Thus a partially initialized
cifsFileInfo structure becomes available to other threads that
walk through the inode's lock list. One example of such a thread
may be an oplock break worker thread that tries to push all
cached byte-range locks. This causes NULL-pointer dereference
in smb2_push_mandatory_locks() when accessing cfile->tlink:
[598428.945633] BUG: kernel NULL pointer dereference, address: 0000000000000038
...
[598428.945749] Workqueue: cifsoplockd cifs_oplock_break [cifs]
[598428.945793] RIP: 0010:smb2_push_mandatory_locks+0xd6/0x5a0 [cifs]
...
[598428.945834] Call Trace:
[598428.945870] ? cifs_revalidate_mapping+0x45/0x90 [cifs]
[598428.945901] cifs_oplock_break+0x13d/0x450 [cifs]
[598428.945909] process_one_work+0x1db/0x380
[598428.945914] worker_thread+0x4d/0x400
[598428.945921] kthread+0x104/0x140
[598428.945925] ? process_one_work+0x380/0x380
[598428.945931] ? kthread_park+0x80/0x80
[598428.945937] ret_from_fork+0x35/0x40
Fix this by reordering initialization steps of the cifsFileInfo
structure: initialize all the fields first and then add the new
byte-range lock list to the inode's lock list.
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
---
fs/cifs/file.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 520fbe4d42b9..069635ec9d94 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -313,9 +313,6 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
INIT_LIST_HEAD(&fdlocks->locks);
fdlocks->cfile = cfile;
cfile->llist = fdlocks;
- cifs_down_write(&cinode->lock_sem);
- list_add(&fdlocks->llist, &cinode->llist);
- up_write(&cinode->lock_sem);
cfile->count = 1;
cfile->pid = current->tgid;
@@ -339,6 +336,10 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
oplock = 0;
}
+ cifs_down_write(&cinode->lock_sem);
+ list_add(&fdlocks->llist, &cinode->llist);
+ up_write(&cinode->lock_sem);
+
spin_lock(&tcon->open_file_lock);
if (fid->pending_open->oplock != CIFS_OPLOCK_NO_CHANGE && oplock)
oplock = fid->pending_open->oplock;
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks
2019-11-28 0:18 [PATCH] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks Pavel Shilovsky
@ 2019-12-01 5:27 ` Steve French
2019-12-02 12:25 ` Aurélien Aptel
1 sibling, 0 replies; 3+ messages in thread
From: Steve French @ 2019-12-01 5:27 UTC (permalink / raw)
To: Pavel Shilovsky; +Cc: CIFS, Long Li
Merged into cifs-2.6.git for-next
On Wed, Nov 27, 2019 at 6:18 PM Pavel Shilovsky <piastryyy@gmail.com> wrote:
>
> Currently when the client creates a cifsFileInfo structure for
> a newly opened file, it allocates a list of byte-range locks
> with a pointer to the new cfile and attaches this list to the
> inode's lock list. The latter happens before initializing all
> other fields, e.g. cfile->tlink. Thus a partially initialized
> cifsFileInfo structure becomes available to other threads that
> walk through the inode's lock list. One example of such a thread
> may be an oplock break worker thread that tries to push all
> cached byte-range locks. This causes NULL-pointer dereference
> in smb2_push_mandatory_locks() when accessing cfile->tlink:
>
> [598428.945633] BUG: kernel NULL pointer dereference, address: 0000000000000038
> ...
> [598428.945749] Workqueue: cifsoplockd cifs_oplock_break [cifs]
> [598428.945793] RIP: 0010:smb2_push_mandatory_locks+0xd6/0x5a0 [cifs]
> ...
> [598428.945834] Call Trace:
> [598428.945870] ? cifs_revalidate_mapping+0x45/0x90 [cifs]
> [598428.945901] cifs_oplock_break+0x13d/0x450 [cifs]
> [598428.945909] process_one_work+0x1db/0x380
> [598428.945914] worker_thread+0x4d/0x400
> [598428.945921] kthread+0x104/0x140
> [598428.945925] ? process_one_work+0x380/0x380
> [598428.945931] ? kthread_park+0x80/0x80
> [598428.945937] ret_from_fork+0x35/0x40
>
> Fix this by reordering initialization steps of the cifsFileInfo
> structure: initialize all the fields first and then add the new
> byte-range lock list to the inode's lock list.
>
> Cc: Stable <stable@vger.kernel.org>
> Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
> ---
> fs/cifs/file.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 520fbe4d42b9..069635ec9d94 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -313,9 +313,6 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
> INIT_LIST_HEAD(&fdlocks->locks);
> fdlocks->cfile = cfile;
> cfile->llist = fdlocks;
> - cifs_down_write(&cinode->lock_sem);
> - list_add(&fdlocks->llist, &cinode->llist);
> - up_write(&cinode->lock_sem);
>
> cfile->count = 1;
> cfile->pid = current->tgid;
> @@ -339,6 +336,10 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
> oplock = 0;
> }
>
> + cifs_down_write(&cinode->lock_sem);
> + list_add(&fdlocks->llist, &cinode->llist);
> + up_write(&cinode->lock_sem);
> +
> spin_lock(&tcon->open_file_lock);
> if (fid->pending_open->oplock != CIFS_OPLOCK_NO_CHANGE && oplock)
> oplock = fid->pending_open->oplock;
> --
> 2.17.1
>
--
Thanks,
Steve
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks
2019-11-28 0:18 [PATCH] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks Pavel Shilovsky
2019-12-01 5:27 ` Steve French
@ 2019-12-02 12:25 ` Aurélien Aptel
1 sibling, 0 replies; 3+ messages in thread
From: Aurélien Aptel @ 2019-12-02 12:25 UTC (permalink / raw)
To: Pavel Shilovsky, Steve French, linux-cifs; +Cc: Long Li
Pavel Shilovsky <piastryyy@gmail.com> writes:
> Currently when the client creates a cifsFileInfo structure for
> a newly opened file, it allocates a list of byte-range locks
> with a pointer to the new cfile and attaches this list to the
> inode's lock list. The latter happens before initializing all
> other fields, e.g. cfile->tlink. Thus a partially initialized
> cifsFileInfo structure becomes available to other threads that
> walk through the inode's lock list. One example of such a thread
> may be an oplock break worker thread that tries to push all
> cached byte-range locks. This causes NULL-pointer dereference
> in smb2_push_mandatory_locks() when accessing cfile->tlink:
reviewing late but this makes sense.
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
--
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-11-28 0:18 [PATCH] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks Pavel Shilovsky
2019-12-01 5:27 ` Steve French
2019-12-02 12:25 ` Aurélien Aptel
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