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| author | Dave Wysochanski <dwysocha@redhat.com> | 2019-10-23 11:02:33 +0200 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2019-10-25 04:35:04 +0200 |
| commit | d46b0da7a33dd8c99d969834f682267a45444ab3 (patch) | |
| tree | f8db814544321af48a968439747c6c39a334de60 /fs/cifs/cifsproto.h | |
| parent | CIFS: Fix use after free of file info structures (diff) | |
| download | linux-d46b0da7a33dd8c99d969834f682267a45444ab3.tar.xz linux-d46b0da7a33dd8c99d969834f682267a45444ab3.zip | |
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/cifsproto.h')
| -rw-r--r-- | fs/cifs/cifsproto.h | 1 |
1 files changed, 1 insertions, 0 deletions
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, |