Looks good. Reviewed-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx> -- Best regards, Pavel Shilovsky ср, 17 июл. 2019 г. в 03:46, Aurelien Aptel <aaptel@xxxxxxxx>: > > 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@xxxxxxxxxxxxxxxxxxxxxxxxx/T/#u > Fixes: 3d4ef9a15343 ("smb3: fix redundant opens on root") > Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx> > --- > > 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@xxxxxxxxxxxxxxxxxxxxxxxxx/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 >
