3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Konstantin Khlebnikov <[email protected]> commit 69abaffec7d47a083739b79e3066cb3730eba72e upstream. Cfq_lookup_create_cfqg() allocates struct blkcg_gq using GFP_ATOMIC. In cfq_find_alloc_queue() possible allocation failure is not handled. As a result kernel oopses on NULL pointer dereference when cfq_link_cfqq_cfqg() calls cfqg_get() for NULL pointer. Bug was introduced in v3.5 in commit cd1604fab4f9 ("blkcg: factor out blkio_group creation"). Prior to that commit cfq group lookup had returned pointer to root group as fallback. This patch handles this error using existing fallback oom_cfqq. Signed-off-by: Konstantin Khlebnikov <[email protected]> Acked-by: Tejun Heo <[email protected]> Acked-by: Vivek Goyal <[email protected]> Fixes: cd1604fab4f9 ("blkcg: factor out blkio_group creation") Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Luis Henriques <[email protected]> --- block/cfq-iosched.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index f3627ca9303b..2c0585adfaea 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3582,6 +3582,11 @@ retry: blkcg = bio_blkcg(bio); cfqg = cfq_lookup_create_cfqg(cfqd, blkcg); + if (!cfqg) { + cfqq = &cfqd->oom_cfqq; + goto out; + } + cfqq = cic_to_cfqq(cic, is_sync); /* @@ -3618,7 +3623,7 @@ retry: } else cfqq = &cfqd->oom_cfqq; } - +out: if (new_cfqq) kmem_cache_free(cfq_pool, new_cfqq); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
