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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Dave Wysochanski <dwysocha@redhat.com>,
	Ronnie Sahlberg <lsahlber@redhat.com>,
	Pavel Shilovsky <pshilov@microsoft.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 17/34] cifs: Fix cifsInodeInfo lock_sem deadlock when reconnect occurs
Date: Fri,  8 Nov 2019 19:50:24 +0100
Message-ID: <20191108174637.779336809@linuxfoundation.org> (raw)
In-Reply-To: <20191108174618.266472504@linuxfoundation.org>

From: Dave Wysochanski <dwysocha@redhat.com>

[ Upstream commit d46b0da7a33dd8c99d969834f682267a45444ab3 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/cifsglob.h  |  5 +++++
 fs/cifs/cifsproto.h |  1 +
 fs/cifs/file.c      | 23 +++++++++++++++--------
 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 5367b684c1f74..7ae21ad420fbf 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1178,6 +1178,11 @@ 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 cd8025a249bba..cdf244df91c25 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -138,6 +138,7 @@ 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 3504ef015493b..1c3f262d9c4d4 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -280,6 +280,13 @@ 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)
@@ -305,7 +312,7 @@ 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);
 
@@ -457,7 +464,7 @@ 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);
@@ -1011,7 +1018,7 @@ 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);
 }
@@ -1033,7 +1040,7 @@ 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, &conf_lock, CIFS_LOCK_OP);
@@ -1055,7 +1062,7 @@ cifs_lock_add_if(struct cifsFileInfo *cfile, struct cifsLockInfo *lock,
 					(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);
 	}
 
@@ -1108,7 +1115,7 @@ 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;
@@ -1312,7 +1319,7 @@ 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;
@@ -1501,7 +1508,7 @@ 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 dee5250701deb..41f1a5dd33a53 100644
--- a/fs/cifs/smb2file.c
+++ b/fs/cifs/smb2file.c
@@ -138,7 +138,7 @@ 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) <
-- 
2.20.1




  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08 18:50 [PATCH 4.9 00/34] 4.9.200-stable review Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 01/34] regulator: ti-abb: Fix timeout in ti_abb_wait_txdone/ti_abb_clear_all_txdone Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 02/34] regulator: pfuze100-regulator: Variable "val" in pfuze100_regulator_probe() could be uninitialized Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 03/34] ASoC: wm_adsp: Dont generate kcontrols without READ flags Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 04/34] ASoc: rockchip: i2s: Fix RPM imbalance Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 05/34] ARM: dts: logicpd-torpedo-som: Remove twl_keypad Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 06/34] pinctrl: ns2: Fix off by one bugs in ns2_pinmux_enable() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 07/34] ARM: mm: fix alignment handler faults under memory pressure Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 08/34] scsi: scsi_dh_alua: handle RTPG sense code correctly during state transitions Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 09/34] scsi: sni_53c710: fix compilation error Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 10/34] scsi: fix kconfig dependency warning related to 53C700_LE_ON_BE Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 11/34] ARM: dts: imx7s: Correct GPTs ipg clock source Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 12/34] perf kmem: Fix memory leak in compact_gfp_flags() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 13/34] ARM: davinci: dm365: Fix McBSP dma_slave_map entry Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 14/34] scsi: target: core: Do not overwrite CDB byte 1 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 15/34] of: unittest: fix memory leak in unittest_data_add Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 16/34] MIPS: bmips: mark exception vectors as char arrays Greg Kroah-Hartman
2019-11-08 18:50 ` Greg Kroah-Hartman [this message]
2019-11-08 18:50 ` [PATCH 4.9 18/34] dccp: do not leak jiffies on the wire Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 19/34] net: fix sk_page_frag() recursion from memory reclaim Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 20/34] net: hisilicon: Fix ping latency when deal with high throughput Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 21/34] net: Zeroing the structure ethtool_wolinfo in ethtool_get_wol() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 22/34] selftests: net: reuseport_dualstack: fix uninitalized parameter Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 23/34] net: add READ_ONCE() annotation in __skb_wait_for_more_packets() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 24/34] net: dsa: fix switch tree list Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 25/34] net: bcmgenet: reset 40nm EPHY on energy detect Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 26/34] vxlan: check tun_info options_len properly Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 27/34] net/mlx4_core: Dynamically set guaranteed amount of counters per VF Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 28/34] inet: stop leaking jiffies on the wire Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 29/34] Kbuild: make designated_init attribute fatal Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 30/34] kbuild: use -fmacro-prefix-map to make __FILE__ a relative path Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 31/34] kbuild: add -fcf-protection=none when using retpoline flags Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 32/34] net/flow_dissector: switch to siphash Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 33/34] dmaengine: qcom: bam_dma: Fix resource leak Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.9 34/34] alarmtimer: Change remaining ENOTSUPP to EOPNOTSUPP Greg Kroah-Hartman
2019-11-09  0:57 ` [PATCH 4.9 00/34] 4.9.200-stable review kernelci.org bot
2019-11-09 10:18 ` Naresh Kamboju
2019-11-09 15:39 ` Guenter Roeck

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