From: xiao jin <jin.xiao@xxxxxxxxx>
commit 54648cf1ec2d7f4b6a71767799c45676a138ca24 upstream
We find the memory use-after-free issue in __blk_drain_queue()
on the kernel 4.14. After read the latest kernel 4.18-rc6 we
think it has the same problem.
Memory is allocated for q->fq in the blk_init_allocated_queue().
If the elevator init function called with error return, it will
run into the fail case to free the q->fq.
Then the __blk_drain_queue() uses the same memory after the free
of the q->fq, it will lead to the unpredictable event.
The patch is to set q->fq as NULL in the fail case of
blk_init_allocated_queue().
Fixes: commit 7c94e1c157a2 ("block: introduce blk_flush_queue to drive flush machinery")
Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxx>
Signed-off-by: xiao jin <jin.xiao@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
[groeck: backport to v4.4.y/v4.9.y (context change)]
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
This patch was not applied to v4.4.y and v4.9.y due to a context conflict.
See https://lore.kernel.org/stable/1536310209129100@xxxxxxxxx/ and
https://lore.kernel.org/stable/153631018011582@xxxxxxxxx/ for details.
It was applied to v4.14.y and to v4.18.y.
Please consider applying this backport. It is relevant because it fixes
CVE-2018-20856.
Thanks,
Guenter
block/blk-core.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/block/blk-core.c b/block/blk-core.c
index 50d77c90070d..7662f97dded6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -870,6 +870,7 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
fail:
blk_free_flush_queue(q->fq);
+ q->fq = NULL;
return NULL;
}
EXPORT_SYMBOL(blk_init_allocated_queue);
--
2.7.4
