diff mbox series

[SRU,E/D/B/X] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks

Message ID 20191219070353.10501-1-juergh@canonical.com
State New
Headers show
Series [SRU,E/D/B/X] CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks | expand

Commit Message

Juerg Haefliger Dec. 19, 2019, 7:03 a.m. UTC 
From: Pavel Shilovsky <pshilov@microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/1856949

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>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
---
 fs/cifs/file.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Connor Kuehl Dec. 20, 2019, 6:47 p.m. UTC | #1 
On 12/18/19 11:03 PM, Juerg Haefliger wrote:
> From: Pavel Shilovsky <pshilov@microsoft.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1856949
> 
> 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>
> Reviewed-by: Aurelien Aptel <aaptel@suse.com>
> Signed-off-by: Steve French <stfrench@microsoft.com>
> Signed-off-by: Juerg Haefliger <juergh@canonical.com>

Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Marcelo Henrique Cerri Jan. 6, 2020, 12:09 p.m. UTC | #2 
Acked-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>

We just need to include the reference to the upstream commit:

(cherry picked from commit 6f582b273ec23332074d970a7fb25bef835df71f)

On Thu, Dec 19, 2019 at 08:03:53AM +0100, Juerg Haefliger wrote:
> From: Pavel Shilovsky <pshilov@microsoft.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1856949
> 
> 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>
> Reviewed-by: Aurelien Aptel <aaptel@suse.com>
> Signed-off-by: Steve French <stfrench@microsoft.com>
> Signed-off-by: Juerg Haefliger <juergh@canonical.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 facb52d37d19..c9abc789c6b5 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;
> -- 
> 2.20.1
> 
> 
> -- 
> kernel-team mailing list
> kernel-team@lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
Kleber Sacilotto de Souza Jan. 6, 2020, 12:36 p.m. UTC | #3 
On 2019-12-19 08:03, Juerg Haefliger wrote:
> From: Pavel Shilovsky <pshilov@microsoft.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1856949
> 
> 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>
> Reviewed-by: Aurelien Aptel <aaptel@suse.com>
> Signed-off-by: Steve French <stfrench@microsoft.com>
> Signed-off-by: Juerg Haefliger <juergh@canonical.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 facb52d37d19..c9abc789c6b5 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;
> 


Applied to xenial/master-next branch.

Already applied to Bionic, Disco and Eoan by upstream stable updates.

Thanks,
Kleber
diff mbox series

Patch

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index facb52d37d19..c9abc789c6b5 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;