diff options
| author | Bart Van Assche <bart.vanassche@wdc.com> | 2017-12-06 03:57:51 +0300 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2017-12-12 05:56:48 +0300 |
| commit | 14e3062fb18532175af4d1c4073597999f7a2248 (patch) | |
| tree | 71d080a04b27eca5b1923ec3b92a057682df574f | |
| parent | 3e5c63565aca5fbd1cc150cb2ca77154fc50fa0c (diff) | |
| download | linux-14e3062fb18532175af4d1c4073597999f7a2248.tar.xz | |
scsi: core: Fix a scsi_show_rq() NULL pointer dereference
Avoid that scsi_show_rq() triggers a NULL pointer dereference if called
after sd_uninit_command(). Swap the NULL pointer assignment and the
mempool_free() call in sd_uninit_command() to make it less likely that
scsi_show_rq() triggers a use-after-free. Note: even with these changes
scsi_show_rq() can trigger a use-after-free but that's a lesser evil
than e.g. suppressing debug information for T10 PI Type 2 commands
completely. This patch fixes the following oops:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: scsi_format_opcode_name+0x1a/0x1c0
CPU: 1 PID: 1881 Comm: cat Not tainted 4.14.0-rc2.blk_mq_io_hang+ #516
Call Trace:
__scsi_format_command+0x27/0xc0
scsi_show_rq+0x5c/0xc0
__blk_mq_debugfs_rq_show+0x116/0x130
blk_mq_debugfs_rq_show+0xe/0x10
seq_read+0xfe/0x3b0
full_proxy_read+0x54/0x90
__vfs_read+0x37/0x160
vfs_read+0x96/0x130
SyS_read+0x55/0xc0
entry_SYSCALL_64_fastpath+0x1a/0xa5
[mkp: added Type 2]
Fixes: 0eebd005dd07 ("scsi: Implement blk_mq_ops.show_rq()")
Reported-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: James E.J. Bottomley <jejb@linux.vnet.ibm.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
| -rw-r--r-- | drivers/scsi/scsi_debugfs.c | 6 | ||||
| -rw-r--r-- | drivers/scsi/sd.c | 4 |
2 files changed, 7 insertions, 3 deletions
diff --git a/drivers/scsi/scsi_debugfs.c b/drivers/scsi/scsi_debugfs.c index 01f08c03f2c1..c3765d29fd3f 100644 --- a/drivers/scsi/scsi_debugfs.c +++ b/drivers/scsi/scsi_debugfs.c @@ -8,9 +8,11 @@ void scsi_show_rq(struct seq_file *m, struct request *rq) { struct scsi_cmnd *cmd = container_of(scsi_req(rq), typeof(*cmd), req); int msecs = jiffies_to_msecs(jiffies - cmd->jiffies_at_alloc); - char buf[80]; + const u8 *const cdb = READ_ONCE(cmd->cmnd); + char buf[80] = "(?)"; - __scsi_format_command(buf, sizeof(buf), cmd->cmnd, cmd->cmd_len); + if (cdb) + __scsi_format_command(buf, sizeof(buf), cdb, cmd->cmd_len); seq_printf(m, ", .cmd=%s, .retries=%d, allocated %d.%03d s ago", buf, cmd->retries, msecs / 1000, msecs % 1000); } diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 24fe68522716..a028ab3322a9 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1312,6 +1312,7 @@ static int sd_init_command(struct scsi_cmnd *cmd) static void sd_uninit_command(struct scsi_cmnd *SCpnt) { struct request *rq = SCpnt->request; + u8 *cmnd; if (SCpnt->flags & SCMD_ZONE_WRITE_LOCK) sd_zbc_write_unlock_zone(SCpnt); @@ -1320,9 +1321,10 @@ static void sd_uninit_command(struct scsi_cmnd *SCpnt) __free_page(rq->special_vec.bv_page); if (SCpnt->cmnd != scsi_req(rq)->cmd) { - mempool_free(SCpnt->cmnd, sd_cdb_pool); + cmnd = SCpnt->cmnd; SCpnt->cmnd = NULL; SCpnt->cmd_len = 0; + mempool_free(cmnd, sd_cdb_pool); } } |