[PATCH v5.10 0/5] bfq bic/cgroup interaction uaf fixes

[PATCH v5.10 0/5] bfq bic/cgroup interaction uaf fixes

[Khazhismel Kumykov]

Pulls in uaf fix for bfqq->bic along with fixups. I pulled in the
backport dependencies that were also present in 5.15-lts.

NeilBrown (1):
  block/bfq-iosched.c: use "false" rather than "BLK_RW_ASYNC"

Yu Kuai (4):
  block, bfq: fix possible uaf for 'bfqq->bic'
  block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq
  block, bfq: replace 0/1 with false/true in bic apis
  block, bfq: fix uaf for bfqq in bic_set_bfqq()

 block/bfq-cgroup.c  |  8 ++++----
 block/bfq-iosched.c | 19 +++++++++++++------
 2 files changed, 17 insertions(+), 10 deletions(-)

-- 
2.40.0.rc1.284.g88254d51c5-goog

[PATCH v5.10 1/5] block, bfq: fix possible uaf for 'bfqq->bic'

[Khazhismel Kumykov]

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 64dc8c732f5c2b406cc752e6aaa1bd5471159cab ]

Our test report a uaf for 'bfqq->bic' in 5.10:

==================================================================
BUG: KASAN: use-after-free in bfq_select_queue+0x378/0xa30

CPU: 6 PID: 2318352 Comm: fsstress Kdump: loaded Not tainted 5.10.0-60.18.0.50.h602.kasan.eulerosv2r11.x86_64 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-20220320_160524-szxrtosci10000 04/01/2014
Call Trace:
 bfq_select_queue+0x378/0xa30
 bfq_dispatch_request+0xe8/0x130
 blk_mq_do_dispatch_sched+0x62/0xb0
 __blk_mq_sched_dispatch_requests+0x215/0x2a0
 blk_mq_sched_dispatch_requests+0x8f/0xd0
 __blk_mq_run_hw_queue+0x98/0x180
 __blk_mq_delay_run_hw_queue+0x22b/0x240
 blk_mq_run_hw_queue+0xe3/0x190
 blk_mq_sched_insert_requests+0x107/0x200
 blk_mq_flush_plug_list+0x26e/0x3c0
 blk_finish_plug+0x63/0x90
 __iomap_dio_rw+0x7b5/0x910
 iomap_dio_rw+0x36/0x80
 ext4_dio_read_iter+0x146/0x190 [ext4]
 ext4_file_read_iter+0x1e2/0x230 [ext4]
 new_sync_read+0x29f/0x400
 vfs_read+0x24e/0x2d0
 ksys_read+0xd5/0x1b0
 do_syscall_64+0x33/0x40
 entry_SYSCALL_64_after_hwframe+0x61/0xc6

Commit 3bc5e683c67d ("bfq: Split shared queues on move between cgroups")
changes that move process to a new cgroup will allocate a new bfqq to
use, however, the old bfqq and new bfqq can point to the same bic:

1) Initial state, two process with io in the same cgroup.

Process 1       Process 2
 (BIC1)          (BIC2)
  |  Λ            |  Λ
  |  |            |  |
  V  |            V  |
  bfqq1           bfqq2

2) bfqq1 is merged to bfqq2.

Process 1       Process 2
 (BIC1)          (BIC2)
  |               |
   \-------------\|
                  V
  bfqq1           bfqq2(coop)

3) Process 1 exit, then issue new io(denoce IOA) from Process 2.

 (BIC2)
  |  Λ
  |  |
  V  |
  bfqq2(coop)

4) Before IOA is completed, move Process 2 to another cgroup and issue io.

Process 2
 (BIC2)
   Λ
   |\--------------\
   |                V
  bfqq2           bfqq3

Now that BIC2 points to bfqq3, while bfqq2 and bfqq3 both point to BIC2.
If all the requests are completed, and Process 2 exit, BIC2 will be
freed while there is no guarantee that bfqq2 will be freed before BIC2.

Fix the problem by clearing bfqq->bic while bfqq is detached from bic.

Fixes: 3bc5e683c67d ("bfq: Split shared queues on move between cgroups")
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221214030430.3304151-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 block/bfq-iosched.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 7c4b8d0635eb..afaededb3c49 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -373,6 +373,12 @@ struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync)
 
 void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync)
 {
+	struct bfq_queue *old_bfqq = bic->bfqq[is_sync];
+
+	/* Clear bic pointer if bfqq is detached from this bic */
+	if (old_bfqq && old_bfqq->bic == bic)
+		old_bfqq->bic = NULL;
+
 	bic->bfqq[is_sync] = bfqq;
 }
 
@@ -4977,7 +4983,6 @@ static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
 		unsigned long flags;
 
 		spin_lock_irqsave(&bfqd->lock, flags);
-		bfqq->bic = NULL;
 		bfq_exit_bfqq(bfqd, bfqq);
 		bic_set_bfqq(bic, NULL, is_sync);
 		spin_unlock_irqrestore(&bfqd->lock, flags);
-- 
2.40.0.rc1.284.g88254d51c5-goog

[PATCH v5.10 2/5] block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq

[Khazhismel Kumykov]

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 246cf66e300b76099b5dbd3fdd39e9a5dbc53f02 ]

Commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
will access 'bic->bfqq' in bic_set_bfqq(), however, bfq_exit_icq_bfqq()
can free bfqq first, and then call bic_set_bfqq(), which will cause uaf.

Fix the problem by moving bfq_exit_bfqq() behind bic_set_bfqq().

Fixes: 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20221226030605.1437081-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 block/bfq-iosched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index afaededb3c49..0a53b653a7e2 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4983,8 +4983,8 @@ static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
 		unsigned long flags;
 
 		spin_lock_irqsave(&bfqd->lock, flags);
-		bfq_exit_bfqq(bfqd, bfqq);
 		bic_set_bfqq(bic, NULL, is_sync);
+		bfq_exit_bfqq(bfqd, bfqq);
 		spin_unlock_irqrestore(&bfqd->lock, flags);
 	}
 }
-- 
2.40.0.rc1.284.g88254d51c5-goog

[PATCH v5.10 3/5] block/bfq-iosched.c: use "false" rather than "BLK_RW_ASYNC"

[Khazhismel Kumykov]

From: NeilBrown <neilb@suse.de>

[ Upstream commit f6bad159f5d5e5b33531aba3d9b860ad8618afe0 ]

bfq_get_queue() expects a "bool" for the third arg, so pass "false"
rather than "BLK_RW_ASYNC" which will soon be removed.

Link: https://lkml.kernel.org/r/164549983746.9187.7949730109246767909.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Paolo Valente <paolo.valente@linaro.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stable-dep-of: b600de2d7d3a ("block, bfq: fix uaf for bfqq in bic_set_bfqq()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 block/bfq-iosched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 0a53b653a7e2..35b240cba092 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5071,7 +5071,7 @@ static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio)
 	bfqq = bic_to_bfqq(bic, false);
 	if (bfqq) {
 		bfq_release_process_ref(bfqd, bfqq);
-		bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic);
+		bfqq = bfq_get_queue(bfqd, bio, false, bic);
 		bic_set_bfqq(bic, bfqq, false);
 	}
 
-- 
2.40.0.rc1.284.g88254d51c5-goog

[PATCH v5.10 4/5] block, bfq: replace 0/1 with false/true in bic apis

[Khazhismel Kumykov]

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 337366e02b370d2800110fbc99940f6ddddcbdfa ]

Just to make the code a litter cleaner, there are no functional changes.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221214033155.3455754-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: b600de2d7d3a ("block, bfq: fix uaf for bfqq in bic_set_bfqq()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 block/bfq-cgroup.c  | 8 ++++----
 block/bfq-iosched.c | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index badb90352bf3..2f440b79183d 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -705,15 +705,15 @@ static void *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
 				     struct bfq_io_cq *bic,
 				     struct bfq_group *bfqg)
 {
-	struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
-	struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
+	struct bfq_queue *async_bfqq = bic_to_bfqq(bic, false);
+	struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, true);
 	struct bfq_entity *entity;
 
 	if (async_bfqq) {
 		entity = &async_bfqq->entity;
 
 		if (entity->sched_data != &bfqg->sched_data) {
-			bic_set_bfqq(bic, NULL, 0);
+			bic_set_bfqq(bic, NULL, false);
 			bfq_release_process_ref(bfqd, async_bfqq);
 		}
 	}
@@ -749,7 +749,7 @@ static void *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
 				 */
 				bfq_put_cooperator(sync_bfqq);
 				bfq_release_process_ref(bfqd, sync_bfqq);
-				bic_set_bfqq(bic, NULL, 1);
+				bic_set_bfqq(bic, NULL, true);
 			}
 		}
 	}
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 35b240cba092..016d7f32af9f 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2816,7 +2816,7 @@ bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
 	/*
 	 * Merge queues (that is, let bic redirect its requests to new_bfqq)
 	 */
-	bic_set_bfqq(bic, new_bfqq, 1);
+	bic_set_bfqq(bic, new_bfqq, true);
 	bfq_mark_bfqq_coop(new_bfqq);
 	/*
 	 * new_bfqq now belongs to at least two bics (it is a shared queue):
@@ -6014,7 +6014,7 @@ bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq)
 		return bfqq;
 	}
 
-	bic_set_bfqq(bic, NULL, 1);
+	bic_set_bfqq(bic, NULL, true);
 
 	bfq_put_cooperator(bfqq);
 
-- 
2.40.0.rc1.284.g88254d51c5-goog

[PATCH v5.10 5/5] block, bfq: fix uaf for bfqq in bic_set_bfqq()

[Khazhismel Kumykov]

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit b600de2d7d3a16f9007fad1bdae82a3951a26af2 ]

After commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'"),
bic->bfqq will be accessed in bic_set_bfqq(), however, in some context
bic->bfqq will be freed, and bic_set_bfqq() is called with the freed
bic->bfqq.

Fix the problem by always freeing bfqq after bic_set_bfqq().

Fixes: 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'")
Reported-and-tested-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230130014136.591038-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 block/bfq-cgroup.c  | 2 +-
 block/bfq-iosched.c | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 2f440b79183d..1f9ccc661d57 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -748,8 +748,8 @@ static void *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
 				 * request from the old cgroup.
 				 */
 				bfq_put_cooperator(sync_bfqq);
-				bfq_release_process_ref(bfqd, sync_bfqq);
 				bic_set_bfqq(bic, NULL, true);
+				bfq_release_process_ref(bfqd, sync_bfqq);
 			}
 		}
 	}
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 016d7f32af9f..6687b805bab3 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5070,9 +5070,11 @@ static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio)
 
 	bfqq = bic_to_bfqq(bic, false);
 	if (bfqq) {
-		bfq_release_process_ref(bfqd, bfqq);
+		struct bfq_queue *old_bfqq = bfqq;
+
 		bfqq = bfq_get_queue(bfqd, bio, false, bic);
 		bic_set_bfqq(bic, bfqq, false);
+		bfq_release_process_ref(bfqd, old_bfqq);
 	}
 
 	bfqq = bic_to_bfqq(bic, true);
-- 
2.40.0.rc1.284.g88254d51c5-goog

Re: [PATCH v5.10 0/5] bfq bic/cgroup interaction uaf fixes

[Sasha Levin]

On Mon, Mar 13, 2023 at 03:27:52PM -0700, Khazhismel Kumykov wrote:
>Pulls in uaf fix for bfqq->bic along with fixups. I pulled in the
>backport dependencies that were also present in 5.15-lts.
>
>NeilBrown (1):
>  block/bfq-iosched.c: use "false" rather than "BLK_RW_ASYNC"
>
>Yu Kuai (4):
>  block, bfq: fix possible uaf for 'bfqq->bic'
>  block, bfq: fix uaf for bfqq in bfq_exit_icq_bfqq
>  block, bfq: replace 0/1 with false/true in bic apis
>  block, bfq: fix uaf for bfqq in bic_set_bfqq()
>
> block/bfq-cgroup.c  |  8 ++++----
> block/bfq-iosched.c | 19 +++++++++++++------
> 2 files changed, 17 insertions(+), 10 deletions(-)

Queued up, thanks!

-- 
Thanks,
Sasha