diff options
author | Dave Wysochanski <dwysocha@redhat.com> | 2019-10-23 05:02:33 -0400 |
---|---|---|
committer | Steve French <stfrench@microsoft.com> | 2019-10-24 21:35:04 -0500 |
commit | d46b0da7a33dd8c99d969834f682267a45444ab3 (patch) | |
tree | f8db814544321af48a968439747c6c39a334de60 /fs/cifs | |
parent | 1a67c415965752879e2e9fad407bc44fc7f25f23 (diff) | |
download | linux-d46b0da7a33dd8c99d969834f682267a45444ab3.tar.bz2 |
cifs: Fix cifsInodeInfo lock_sem deadlock when reconnect occurs
There's a deadlock that is possible and can easily be seen with
a test where multiple readers open/read/close of the same file
and a disruption occurs causing reconnect. The deadlock is due
a reader thread inside cifs_strict_readv calling down_read and
obtaining lock_sem, and then after reconnect inside
cifs_reopen_file calling down_read a second time. If in
between the two down_read calls, a down_write comes from
another process, deadlock occurs.
CPU0 CPU1
---- ----
cifs_strict_readv()
down_read(&cifsi->lock_sem);
_cifsFileInfo_put
OR
cifs_new_fileinfo
down_write(&cifsi->lock_sem);
cifs_reopen_file()
down_read(&cifsi->lock_sem);
Fix the above by changing all down_write(lock_sem) calls to
down_write_trylock(lock_sem)/msleep() loop, which in turn
makes the second down_read call benign since it will never
block behind the writer while holding lock_sem.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Suggested-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed--by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Diffstat (limited to 'fs/cifs')
-rw-r--r-- | fs/cifs/cifsglob.h | 5 | ||||
-rw-r--r-- | fs/cifs/cifsproto.h | 1 | ||||
-rw-r--r-- | fs/cifs/file.c | 23 | ||||
-rw-r--r-- | fs/cifs/smb2file.c | 2 |
4 files changed, 22 insertions, 9 deletions
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 50dfd9049370..d78bfcc19156 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1391,6 +1391,11 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file); struct cifsInodeInfo { bool can_cache_brlcks; struct list_head llist; /* locks helb by this inode */ + /* + * NOTE: Some code paths call down_read(lock_sem) twice, so + * we must always use use cifs_down_write() instead of down_write() + * for this semaphore to avoid deadlocks. + */ struct rw_semaphore lock_sem; /* protect the fields above */ /* BB add in lists for dirty pages i.e. write caching info for oplock */ struct list_head openFileList; diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index e53e9f62b87b..fe597d3d5208 100644 --- a/fs/cifs/cifsproto.h +++ b/fs/cifs/cifsproto.h @@ -170,6 +170,7 @@ extern int cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, const unsigned int xid); extern int cifs_push_mandatory_locks(struct cifsFileInfo *cfile); +extern void cifs_down_write(struct rw_semaphore *sem); extern struct cifsFileInfo *cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, struct tcon_link *tlink, diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 64827938ecf7..fa7b0fa72bb3 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -281,6 +281,13 @@ cifs_has_mand_locks(struct cifsInodeInfo *cinode) return has_locks; } +void +cifs_down_write(struct rw_semaphore *sem) +{ + while (!down_write_trylock(sem)) + msleep(10); +} + struct cifsFileInfo * cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, struct tcon_link *tlink, __u32 oplock) @@ -306,7 +313,7 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, INIT_LIST_HEAD(&fdlocks->locks); fdlocks->cfile = cfile; cfile->llist = fdlocks; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_add(&fdlocks->llist, &cinode->llist); up_write(&cinode->lock_sem); @@ -464,7 +471,7 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler) * Delete any outstanding lock records. We'll lose them when the file * is closed anyway. */ - down_write(&cifsi->lock_sem); + cifs_down_write(&cifsi->lock_sem); list_for_each_entry_safe(li, tmp, &cifs_file->llist->locks, llist) { list_del(&li->llist); cifs_del_lock_waiters(li); @@ -1027,7 +1034,7 @@ static void cifs_lock_add(struct cifsFileInfo *cfile, struct cifsLockInfo *lock) { struct cifsInodeInfo *cinode = CIFS_I(d_inode(cfile->dentry)); - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_add_tail(&lock->llist, &cfile->llist->locks); up_write(&cinode->lock_sem); } @@ -1049,7 +1056,7 @@ cifs_lock_add_if(struct cifsFileInfo *cfile, struct cifsLockInfo *lock, try_again: exist = false; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); exist = cifs_find_lock_conflict(cfile, lock->offset, lock->length, lock->type, lock->flags, &conf_lock, @@ -1072,7 +1079,7 @@ try_again: (lock->blist.next == &lock->blist)); if (!rc) goto try_again; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_del_init(&lock->blist); } @@ -1125,7 +1132,7 @@ cifs_posix_lock_set(struct file *file, struct file_lock *flock) return rc; try_again: - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); if (!cinode->can_cache_brlcks) { up_write(&cinode->lock_sem); return rc; @@ -1331,7 +1338,7 @@ cifs_push_locks(struct cifsFileInfo *cfile) int rc = 0; /* we are going to update can_cache_brlcks here - need a write access */ - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); if (!cinode->can_cache_brlcks) { up_write(&cinode->lock_sem); return rc; @@ -1522,7 +1529,7 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, if (!buf) return -ENOMEM; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); for (i = 0; i < 2; i++) { cur = buf; num = 0; diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c index e6a1fc72018f..8b0b512c5792 100644 --- a/fs/cifs/smb2file.c +++ b/fs/cifs/smb2file.c @@ -145,7 +145,7 @@ smb2_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock, cur = buf; - down_write(&cinode->lock_sem); + cifs_down_write(&cinode->lock_sem); list_for_each_entry_safe(li, tmp, &cfile->llist->locks, llist) { if (flock->fl_start > li->offset || (flock->fl_start + length) < |