* [PATCH v1] CIFS: fix deadlock in cached root handling
@ 2019-07-17 10:46 Aurelien Aptel
2019-07-17 18:37 ` Pavel Shilovsky
0 siblings, 1 reply; 3+ messages in thread
From: Aurelien Aptel @ 2019-07-17 10:46 UTC (permalink / raw)
To: linux-cifs; +Cc: piastryyy, Aurelien Aptel
Prevent deadlock between open_shroot() and
cifs_mark_open_files_invalid() by releasing the lock before entering
SMB2_open, taking it again after and checking if we still need to use
the result.
Link: https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u
Fixes: 3d4ef9a15343 ("smb3: fix redundant opens on root")
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
---
this is the for-next version of the patch I sent in the thread
https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u
fs/cifs/smb2ops.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 45 insertions(+), 1 deletion(-)
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 6cb4def11ebe..8202c996b55e 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -694,8 +694,51 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
smb2_set_related(&rqst[1]);
+ /*
+ * We do not hold the lock for the open because in case
+ * SMB2_open needs to reconnect, it will end up calling
+ * cifs_mark_open_files_invalid() which takes the lock again
+ * thus causing a deadlock
+ */
+
+ mutex_unlock(&tcon->crfid.fid_mutex);
rc = compound_send_recv(xid, ses, flags, 2, rqst,
resp_buftype, rsp_iov);
+ mutex_lock(&tcon->crfid.fid_mutex);
+
+ /*
+ * Now we need to check again as the cached root might have
+ * been successfully re-opened from a concurrent process
+ */
+
+ if (tcon->crfid.is_valid) {
+ /* work was already done */
+
+ /* stash fids for close() later */
+ struct cifs_fid fid = {
+ .persistent_fid = pfid->persistent_fid,
+ .volatile_fid = pfid->volatile_fid,
+ };
+
+ /*
+ * caller expects this func to set pfid to a valid
+ * cached root, so we copy the existing one and get a
+ * reference.
+ */
+ memcpy(pfid, tcon->crfid.fid, sizeof(*pfid));
+ kref_get(&tcon->crfid.refcount);
+
+ mutex_unlock(&tcon->crfid.fid_mutex);
+
+ if (rc == 0) {
+ /* close extra handle outside of crit sec */
+ SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
+ }
+ goto oshr_free;
+ }
+
+ /* Cached root is still invalid, continue normaly */
+
if (rc)
goto oshr_exit;
@@ -729,8 +772,9 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
(char *)&tcon->crfid.file_all_info))
tcon->crfid.file_all_info_is_valid = 1;
- oshr_exit:
+oshr_exit:
mutex_unlock(&tcon->crfid.fid_mutex);
+oshr_free:
SMB2_open_free(&rqst[0]);
SMB2_query_info_free(&rqst[1]);
free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);
--
2.16.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v1] CIFS: fix deadlock in cached root handling
2019-07-17 10:46 [PATCH v1] CIFS: fix deadlock in cached root handling Aurelien Aptel
@ 2019-07-17 18:37 ` Pavel Shilovsky
2019-07-18 7:55 ` Steve French
0 siblings, 1 reply; 3+ messages in thread
From: Pavel Shilovsky @ 2019-07-17 18:37 UTC (permalink / raw)
To: Aurelien Aptel; +Cc: linux-cifs
Looks good.
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
--
Best regards,
Pavel Shilovsky
ср, 17 июл. 2019 г. в 03:46, Aurelien Aptel <aaptel@suse.com>:
>
> Prevent deadlock between open_shroot() and
> cifs_mark_open_files_invalid() by releasing the lock before entering
> SMB2_open, taking it again after and checking if we still need to use
> the result.
>
> Link: https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u
> Fixes: 3d4ef9a15343 ("smb3: fix redundant opens on root")
> Signed-off-by: Aurelien Aptel <aaptel@suse.com>
> ---
>
> this is the for-next version of the patch I sent in the thread
> https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u
>
>
> fs/cifs/smb2ops.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 45 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index 6cb4def11ebe..8202c996b55e 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -694,8 +694,51 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
>
> smb2_set_related(&rqst[1]);
>
> + /*
> + * We do not hold the lock for the open because in case
> + * SMB2_open needs to reconnect, it will end up calling
> + * cifs_mark_open_files_invalid() which takes the lock again
> + * thus causing a deadlock
> + */
> +
> + mutex_unlock(&tcon->crfid.fid_mutex);
> rc = compound_send_recv(xid, ses, flags, 2, rqst,
> resp_buftype, rsp_iov);
> + mutex_lock(&tcon->crfid.fid_mutex);
> +
> + /*
> + * Now we need to check again as the cached root might have
> + * been successfully re-opened from a concurrent process
> + */
> +
> + if (tcon->crfid.is_valid) {
> + /* work was already done */
> +
> + /* stash fids for close() later */
> + struct cifs_fid fid = {
> + .persistent_fid = pfid->persistent_fid,
> + .volatile_fid = pfid->volatile_fid,
> + };
> +
> + /*
> + * caller expects this func to set pfid to a valid
> + * cached root, so we copy the existing one and get a
> + * reference.
> + */
> + memcpy(pfid, tcon->crfid.fid, sizeof(*pfid));
> + kref_get(&tcon->crfid.refcount);
> +
> + mutex_unlock(&tcon->crfid.fid_mutex);
> +
> + if (rc == 0) {
> + /* close extra handle outside of crit sec */
> + SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
> + }
> + goto oshr_free;
> + }
> +
> + /* Cached root is still invalid, continue normaly */
> +
> if (rc)
> goto oshr_exit;
>
> @@ -729,8 +772,9 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
> (char *)&tcon->crfid.file_all_info))
> tcon->crfid.file_all_info_is_valid = 1;
>
> - oshr_exit:
> +oshr_exit:
> mutex_unlock(&tcon->crfid.fid_mutex);
> +oshr_free:
> SMB2_open_free(&rqst[0]);
> SMB2_query_info_free(&rqst[1]);
> free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);
> --
> 2.16.4
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v1] CIFS: fix deadlock in cached root handling
2019-07-17 18:37 ` Pavel Shilovsky
@ 2019-07-18 7:55 ` Steve French
0 siblings, 0 replies; 3+ messages in thread
From: Steve French @ 2019-07-18 7:55 UTC (permalink / raw)
To: Pavel Shilovsky; +Cc: Aurelien Aptel, linux-cifs
added cc: stable and made minor cleanup of missing tab
On Wed, Jul 17, 2019 at 1:38 PM Pavel Shilovsky <piastryyy@gmail.com> wrote:
>
> Looks good.
>
> Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
>
> --
> Best regards,
> Pavel Shilovsky
>
> ср, 17 июл. 2019 г. в 03:46, Aurelien Aptel <aaptel@suse.com>:
> >
> > Prevent deadlock between open_shroot() and
> > cifs_mark_open_files_invalid() by releasing the lock before entering
> > SMB2_open, taking it again after and checking if we still need to use
> > the result.
> >
> > Link: https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u
> > Fixes: 3d4ef9a15343 ("smb3: fix redundant opens on root")
> > Signed-off-by: Aurelien Aptel <aaptel@suse.com>
> > ---
> >
> > this is the for-next version of the patch I sent in the thread
> > https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u
> >
> >
> > fs/cifs/smb2ops.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 45 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> > index 6cb4def11ebe..8202c996b55e 100644
> > --- a/fs/cifs/smb2ops.c
> > +++ b/fs/cifs/smb2ops.c
> > @@ -694,8 +694,51 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
> >
> > smb2_set_related(&rqst[1]);
> >
> > + /*
> > + * We do not hold the lock for the open because in case
> > + * SMB2_open needs to reconnect, it will end up calling
> > + * cifs_mark_open_files_invalid() which takes the lock again
> > + * thus causing a deadlock
> > + */
> > +
> > + mutex_unlock(&tcon->crfid.fid_mutex);
> > rc = compound_send_recv(xid, ses, flags, 2, rqst,
> > resp_buftype, rsp_iov);
> > + mutex_lock(&tcon->crfid.fid_mutex);
> > +
> > + /*
> > + * Now we need to check again as the cached root might have
> > + * been successfully re-opened from a concurrent process
> > + */
> > +
> > + if (tcon->crfid.is_valid) {
> > + /* work was already done */
> > +
> > + /* stash fids for close() later */
> > + struct cifs_fid fid = {
> > + .persistent_fid = pfid->persistent_fid,
> > + .volatile_fid = pfid->volatile_fid,
> > + };
> > +
> > + /*
> > + * caller expects this func to set pfid to a valid
> > + * cached root, so we copy the existing one and get a
> > + * reference.
> > + */
> > + memcpy(pfid, tcon->crfid.fid, sizeof(*pfid));
> > + kref_get(&tcon->crfid.refcount);
> > +
> > + mutex_unlock(&tcon->crfid.fid_mutex);
> > +
> > + if (rc == 0) {
> > + /* close extra handle outside of crit sec */
> > + SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
> > + }
> > + goto oshr_free;
> > + }
> > +
> > + /* Cached root is still invalid, continue normaly */
> > +
> > if (rc)
> > goto oshr_exit;
> >
> > @@ -729,8 +772,9 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
> > (char *)&tcon->crfid.file_all_info))
> > tcon->crfid.file_all_info_is_valid = 1;
> >
> > - oshr_exit:
> > +oshr_exit:
> > mutex_unlock(&tcon->crfid.fid_mutex);
> > +oshr_free:
> > SMB2_open_free(&rqst[0]);
> > SMB2_query_info_free(&rqst[1]);
> > free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);
> > --
> > 2.16.4
> >
--
Thanks,
Steve
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-07-18 7:55 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2019-07-17 10:46 [PATCH v1] CIFS: fix deadlock in cached root handling Aurelien Aptel
2019-07-17 18:37 ` Pavel Shilovsky
2019-07-18 7:55 ` Steve French
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox