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authorBart Van Assche <bart.vanassche@wdc.com>2017-12-05 16:57:51 -0800
committerMartin K. Petersen <martin.petersen@oracle.com>2017-12-11 21:56:48 -0500
commit14e3062fb18532175af4d1c4073597999f7a2248 (patch)
tree71d080a04b27eca5b1923ec3b92a057682df574f /drivers/scsi/sd.c
parent3e5c63565aca5fbd1cc150cb2ca77154fc50fa0c (diff)
downloadlinux-14e3062fb18532175af4d1c4073597999f7a2248.tar.bz2
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>
Diffstat (limited to 'drivers/scsi/sd.c')
-rw-r--r--drivers/scsi/sd.c4
1 files changed, 3 insertions, 1 deletions
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);
}
}