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authorMaurizio Lombardi <mlombard@redhat.com>2018-03-09 13:59:06 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-05-30 07:47:42 +0200
commit0fdfc3f543261cd112b84b1085e1378c396de302 (patch)
parent67fa45618e2b92d092eace452c71e69624ca187c (diff)
cdrom: do not call check_disk_change() inside cdrom_open()
[ Upstream commit 2bbea6e117357d17842114c65e9a9cf2d13ae8a3 ] when mounting an ISO filesystem sometimes (very rarely) the system hangs because of a race condition between two tasks. PID: 6766 TASK: ffff88007b2a6dd0 CPU: 0 COMMAND: "mount" #0 [ffff880078447ae0] __schedule at ffffffff8168d605 #1 [ffff880078447b48] schedule_preempt_disabled at ffffffff8168ed49 #2 [ffff880078447b58] __mutex_lock_slowpath at ffffffff8168c995 #3 [ffff880078447bb8] mutex_lock at ffffffff8168bdef #4 [ffff880078447bd0] sr_block_ioctl at ffffffffa00b6818 [sr_mod] #5 [ffff880078447c10] blkdev_ioctl at ffffffff812fea50 #6 [ffff880078447c70] ioctl_by_bdev at ffffffff8123a8b3 #7 [ffff880078447c90] isofs_fill_super at ffffffffa04fb1e1 [isofs] #8 [ffff880078447da8] mount_bdev at ffffffff81202570 #9 [ffff880078447e18] isofs_mount at ffffffffa04f9828 [isofs] #10 [ffff880078447e28] mount_fs at ffffffff81202d09 #11 [ffff880078447e70] vfs_kern_mount at ffffffff8121ea8f #12 [ffff880078447ea8] do_mount at ffffffff81220fee #13 [ffff880078447f28] sys_mount at ffffffff812218d6 #14 [ffff880078447f80] system_call_fastpath at ffffffff81698c49 RIP: 00007fd9ea914e9a RSP: 00007ffd5d9bf648 RFLAGS: 00010246 RAX: 00000000000000a5 RBX: ffffffff81698c49 RCX: 0000000000000010 RDX: 00007fd9ec2bc210 RSI: 00007fd9ec2bc290 RDI: 00007fd9ec2bcf30 RBP: 0000000000000000 R8: 0000000000000000 R9: 0000000000000010 R10: 00000000c0ed0001 R11: 0000000000000206 R12: 00007fd9ec2bc040 R13: 00007fd9eb6b2380 R14: 00007fd9ec2bc210 R15: 00007fd9ec2bcf30 ORIG_RAX: 00000000000000a5 CS: 0033 SS: 002b This task was trying to mount the cdrom. It allocated and configured a super_block struct and owned the write-lock for the super_block->s_umount rwsem. While exclusively owning the s_umount lock, it called sr_block_ioctl and waited to acquire the global sr_mutex lock. PID: 6785 TASK: ffff880078720fb0 CPU: 0 COMMAND: "systemd-udevd" #0 [ffff880078417898] __schedule at ffffffff8168d605 #1 [ffff880078417900] schedule at ffffffff8168dc59 #2 [ffff880078417910] rwsem_down_read_failed at ffffffff8168f605 #3 [ffff880078417980] call_rwsem_down_read_failed at ffffffff81328838 #4 [ffff8800784179d0] down_read at ffffffff8168cde0 #5 [ffff8800784179e8] get_super at ffffffff81201cc7 #6 [ffff880078417a10] __invalidate_device at ffffffff8123a8de #7 [ffff880078417a40] flush_disk at ffffffff8123a94b #8 [ffff880078417a88] check_disk_change at ffffffff8123ab50 #9 [ffff880078417ab0] cdrom_open at ffffffffa00a29e1 [cdrom] #10 [ffff880078417b68] sr_block_open at ffffffffa00b6f9b [sr_mod] #11 [ffff880078417b98] __blkdev_get at ffffffff8123ba86 #12 [ffff880078417bf0] blkdev_get at ffffffff8123bd65 #13 [ffff880078417c78] blkdev_open at ffffffff8123bf9b #14 [ffff880078417c90] do_dentry_open at ffffffff811fc7f7 #15 [ffff880078417cd8] vfs_open at ffffffff811fc9cf #16 [ffff880078417d00] do_last at ffffffff8120d53d #17 [ffff880078417db0] path_openat at ffffffff8120e6b2 #18 [ffff880078417e48] do_filp_open at ffffffff8121082b #19 [ffff880078417f18] do_sys_open at ffffffff811fdd33 #20 [ffff880078417f70] sys_open at ffffffff811fde4e #21 [ffff880078417f80] system_call_fastpath at ffffffff81698c49 RIP: 00007f29438b0c20 RSP: 00007ffc76624b78 RFLAGS: 00010246 RAX: 0000000000000002 RBX: ffffffff81698c49 RCX: 0000000000000000 RDX: 00007f2944a5fa70 RSI: 00000000000a0800 RDI: 00007f2944a5fa70 RBP: 00007f2944a5f540 R8: 0000000000000000 R9: 0000000000000020 R10: 00007f2943614c40 R11: 0000000000000246 R12: ffffffff811fde4e R13: ffff880078417f78 R14: 000000000000000c R15: 00007f2944a4b010 ORIG_RAX: 0000000000000002 CS: 0033 SS: 002b This task tried to open the cdrom device, the sr_block_open function acquired the global sr_mutex lock. The call to check_disk_change() then saw an event flag indicating a possible media change and tried to flush any cached data for the device. As part of the flush, it tried to acquire the super_block->s_umount lock associated with the cdrom device. This was the same super_block as created and locked by the previous task. The first task acquires the s_umount lock and then the sr_mutex_lock; the second task acquires the sr_mutex_lock and then the s_umount lock. This patch fixes the issue by moving check_disk_change() out of cdrom_open() and let the caller take care of it. Signed-off-by: Maurizio Lombardi <mlombard@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5 files changed, 9 insertions, 3 deletions
diff --git a/drivers/block/paride/pcd.c b/drivers/block/paride/pcd.c
index 3b7c9f1be484..9c981f600d24 100644
--- a/drivers/block/paride/pcd.c
+++ b/drivers/block/paride/pcd.c
@@ -229,6 +229,8 @@ static int pcd_block_open(struct block_device *bdev, fmode_t mode)
struct pcd_unit *cd = bdev->bd_disk->private_data;
int ret;
+ check_disk_change(bdev);
ret = cdrom_open(&cd->info, bdev, mode);
diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index 3922ce87c2e4..998991a365b8 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -1153,9 +1153,6 @@ int cdrom_open(struct cdrom_device_info *cdi, struct block_device *bdev,
cd_dbg(CD_OPEN, "entering cdrom_open\n");
- /* open is event synchronization point, check events first */
- check_disk_change(bdev);
/* if this was a O_NONBLOCK open and we should honor the flags,
* do a quick open without drive/disc integrity checks. */
diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
index 584bc3126403..e2808fefbb78 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -497,6 +497,9 @@ static struct cdrom_device_ops gdrom_ops = {
static int gdrom_bdops_open(struct block_device *bdev, fmode_t mode)
int ret;
+ check_disk_change(bdev);
ret = cdrom_open(gd.cd_info, bdev, mode);
diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index 0b510bafd90e..99cb9fa2d135 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -1593,6 +1593,8 @@ static int idecd_open(struct block_device *bdev, fmode_t mode)
struct cdrom_info *info;
int rc = -ENXIO;
+ check_disk_change(bdev);
info = ide_cd_get(bdev->bd_disk);
if (!info)
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index acadb6982811..ff243f88d878 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -522,6 +522,8 @@ static int sr_block_open(struct block_device *bdev, fmode_t mode)
struct scsi_cd *cd;
int ret = -ENXIO;
+ check_disk_change(bdev);
cd = scsi_cd_get(bdev->bd_disk);
if (cd) {