diff options
| author | Calvin Owens <calvinowens@fb.com> | 2015-10-30 16:57:00 -0700 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2015-11-02 23:51:25 -0500 |
| commit | f3951a3709ff50990bf3e188c27d346792103432 (patch) | |
| tree | 4579b9af7af6012d4f3cb6268341fa4b1f0e218c /drivers/scsi/sg.c | |
| parent | c913df3f3d6f7f5e5ed845e2786b0fc98a41482f (diff) | |
sg: Fix double-free when drives detach during SG_IO
In sg_common_write(), we free the block request and return -ENODEV if
the device is detached in the middle of the SG_IO ioctl().
Unfortunately, sg_finish_rem_req() also tries to free srp->rq, so we
end up freeing rq->cmd in the already free rq object, and then free
the object itself out from under the current user.
This ends up corrupting random memory via the list_head on the rq
object. The most common crash trace I saw is this:
------------[ cut here ]------------
kernel BUG at block/blk-core.c:1420!
Call Trace:
[<ffffffff81281eab>] blk_put_request+0x5b/0x80
[<ffffffffa0069e5b>] sg_finish_rem_req+0x6b/0x120 [sg]
[<ffffffffa006bcb9>] sg_common_write.isra.14+0x459/0x5a0 [sg]
[<ffffffff8125b328>] ? selinux_file_alloc_security+0x48/0x70
[<ffffffffa006bf95>] sg_new_write.isra.17+0x195/0x2d0 [sg]
[<ffffffffa006cef4>] sg_ioctl+0x644/0xdb0 [sg]
[<ffffffff81170f80>] do_vfs_ioctl+0x90/0x520
[<ffffffff81258967>] ? file_has_perm+0x97/0xb0
[<ffffffff811714a1>] SyS_ioctl+0x91/0xb0
[<ffffffff81602afb>] tracesys+0xdd/0xe2
RIP [<ffffffff81281e04>] __blk_put_request+0x154/0x1a0
The solution is straightforward: just set srp->rq to NULL in the
failure branch so that sg_finish_rem_req() doesn't attempt to re-free
it.
Additionally, since sg_rq_end_io() will never be called on the object
when this happens, we need to free memory backing ->cmd if it isn't
embedded in the object itself.
KASAN was extremely helpful in finding the root cause of this bug.
Signed-off-by: Calvin Owens <calvinowens@fb.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/scsi/sg.c')
| -rw-r--r-- | drivers/scsi/sg.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 9d7b7db75e4b..503ab8b46c0b 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -787,8 +787,14 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp, return k; /* probably out of space --> ENOMEM */ } if (atomic_read(&sdp->detaching)) { - if (srp->bio) + if (srp->bio) { + if (srp->rq->cmd != srp->rq->__cmd) + kfree(srp->rq->cmd); + blk_end_request_all(srp->rq, -EIO); + srp->rq = NULL; + } + sg_finish_rem_req(srp); return -ENODEV; } |