| Message ID | 20190717104628.21400-1-aaptel@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v1] CIFS: fix deadlock in cached root handling | expand |
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 >
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 > >
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);
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(-)