git bisect shows that commit 54a88eb838d3
("block: add single bio async direct IO helper")
causes the following UAF: KASAN: use-after-free Write in io_submit_one
Tried to root-cause the issue, but need the patch submitter's help in
coming up with a fix.
Needed to revert commit 1bb6b8102945
("block: avoid extra iter advance with async iocb")
in order to be able to revert 54a88eb838d37af930c9f19e1930a4fba6789cb5.
George Kennedy (2):
Revert "block: avoid extra iter advance with async iocb"
Revert "block: add single bio async direct IO helper"
block/bio.c | 2 +-
block/fops.c | 96 ++---------------------------------------------------
include/linux/bio.h | 1 -
3 files changed, 4 insertions(+), 95 deletions(-)
--
1.8.3.1
This reverts commit 1bb6b81029456f4e2e6727c5167f43bdfc34bee5.
Revert this commit in order to be able to revert
commit 54a88eb838d3 ("block: add single bio async direct IO helper")
Reported-by: syzkaller <[email protected]>
Signed-off-by: George Kennedy <[email protected]>
---
block/bio.c | 2 +-
block/fops.c | 20 +++++---------------
include/linux/bio.h | 1 -
3 files changed, 6 insertions(+), 17 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 15ab0d6..ead1f8a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1046,7 +1046,7 @@ void __bio_release_pages(struct bio *bio, bool mark_dirty)
}
EXPORT_SYMBOL_GPL(__bio_release_pages);
-void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter)
+static void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter)
{
size_t size = iov_iter_count(iter);
diff --git a/block/fops.c b/block/fops.c
index ad732a3..e73167b 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -329,21 +329,11 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
bio->bi_end_io = blkdev_bio_end_io_async;
bio->bi_ioprio = iocb->ki_ioprio;
- if (iov_iter_is_bvec(iter)) {
- /*
- * Users don't rely on the iterator being in any particular
- * state for async I/O returning -EIOCBQUEUED, hence we can
- * avoid expensive iov_iter_advance(). Bypass
- * bio_iov_iter_get_pages() and set the bvec directly.
- */
- bio_iov_bvec_set(bio, iter);
- } else {
- ret = bio_iov_iter_get_pages(bio, iter);
- if (unlikely(ret)) {
- bio->bi_status = BLK_STS_IOERR;
- bio_endio(bio);
- return ret;
- }
+ ret = bio_iov_iter_get_pages(bio, iter);
+ if (unlikely(ret)) {
+ bio->bi_status = BLK_STS_IOERR;
+ bio_endio(bio);
+ return ret;
}
dio->size = bio->bi_iter.bi_size;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index fe6bdfb..c88700d 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -417,7 +417,6 @@ int bio_add_zone_append_page(struct bio *bio, struct page *page,
void __bio_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int off);
int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter);
-void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter);
void __bio_release_pages(struct bio *bio, bool mark_dirty);
extern void bio_set_pages_dirty(struct bio *bio);
extern void bio_check_pages_dirty(struct bio *bio);
--
1.8.3.1
This reverts commit 54a88eb838d37af930c9f19e1930a4fba6789cb5.
git bisect shows that commit 54a88eb838d3 ("block: add single bio async
direct IO helper") causes the following UAF:
BUG: KASAN: use-after-free in io_submit_one+0x496/0x2fe0 fs/aio.c:1882
Write of size 4 at addr ffff888027c338a0 by task syz-executor873/15100
CPU: 2 PID: 15100 Comm: syz-executor873 Not tainted 5.16.0-rc1-syzk #1
Hardware name: Red Hat KVM, BIOS
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106
print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold.14+0x7d/0x117 mm/kasan/report.c:450
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x18e/0x1f0 mm/kasan/generic.c:189
__kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_fetch_sub_release
include/linux/atomic/atomic-instrumented.h:167 [inline]
__refcount_sub_and_test include/linux/refcount.h:272 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
iocb_put fs/aio.c:1161 [inline]
io_submit_one+0x496/0x2fe0 fs/aio.c:1882
__do_sys_io_submit fs/aio.c:1938 [inline]
__se_sys_io_submit fs/aio.c:1908 [inline]
__x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Conflicts:
block/fops.c
Reported-by: syzkaller <[email protected]>
Signed-off-by: George Kennedy <[email protected]>
---
block/fops.c | 86 +++---------------------------------------------------------
1 file changed, 3 insertions(+), 83 deletions(-)
diff --git a/block/fops.c b/block/fops.c
index e73167b..88e0401 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -282,84 +282,6 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
return ret;
}
-static void blkdev_bio_end_io_async(struct bio *bio)
-{
- struct blkdev_dio *dio = container_of(bio, struct blkdev_dio, bio);
- struct kiocb *iocb = dio->iocb;
- ssize_t ret;
-
- if (likely(!bio->bi_status)) {
- ret = dio->size;
- iocb->ki_pos += ret;
- } else {
- ret = blk_status_to_errno(bio->bi_status);
- }
-
- iocb->ki_complete(iocb, ret);
-
- if (dio->flags & DIO_SHOULD_DIRTY) {
- bio_check_pages_dirty(bio);
- } else {
- bio_release_pages(bio, false);
- bio_put(bio);
- }
-}
-
-static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
- struct iov_iter *iter,
- unsigned int nr_pages)
-{
- struct block_device *bdev = iocb->ki_filp->private_data;
- struct blkdev_dio *dio;
- struct bio *bio;
- loff_t pos = iocb->ki_pos;
- int ret = 0;
-
- if ((pos | iov_iter_alignment(iter)) &
- (bdev_logical_block_size(bdev) - 1))
- return -EINVAL;
-
- bio = bio_alloc_kiocb(iocb, nr_pages, &blkdev_dio_pool);
- dio = container_of(bio, struct blkdev_dio, bio);
- dio->flags = 0;
- dio->iocb = iocb;
- bio_set_dev(bio, bdev);
- bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
- bio->bi_write_hint = iocb->ki_hint;
- bio->bi_end_io = blkdev_bio_end_io_async;
- bio->bi_ioprio = iocb->ki_ioprio;
-
- ret = bio_iov_iter_get_pages(bio, iter);
- if (unlikely(ret)) {
- bio->bi_status = BLK_STS_IOERR;
- bio_endio(bio);
- return ret;
- }
- dio->size = bio->bi_iter.bi_size;
-
- if (iov_iter_rw(iter) == READ) {
- bio->bi_opf = REQ_OP_READ;
- if (iter_is_iovec(iter)) {
- dio->flags |= DIO_SHOULD_DIRTY;
- bio_set_pages_dirty(bio);
- }
- } else {
- bio->bi_opf = dio_bio_write_op(iocb);
- task_io_account_write(bio->bi_iter.bi_size);
- }
-
- if (iocb->ki_flags & IOCB_HIPRI) {
- bio->bi_opf |= REQ_POLLED | REQ_NOWAIT;
- submit_bio(bio);
- WRITE_ONCE(iocb->private, bio);
- } else {
- if (iocb->ki_flags & IOCB_NOWAIT)
- bio->bi_opf |= REQ_NOWAIT;
- submit_bio(bio);
- }
- return -EIOCBQUEUED;
-}
-
static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
unsigned int nr_pages;
@@ -368,11 +290,9 @@ static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
return 0;
nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS + 1);
- if (likely(nr_pages <= BIO_MAX_VECS)) {
- if (is_sync_kiocb(iocb))
- return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
- return __blkdev_direct_IO_async(iocb, iter, nr_pages);
- }
+ if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_VECS)
+ return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
+
return __blkdev_direct_IO(iocb, iter, bio_max_segs(nr_pages));
}
--
1.8.3.1
On 12/7/21 15:51, George Kennedy wrote:
> git bisect shows that commit 54a88eb838d3
> ("block: add single bio async direct IO helper")
> causes the following UAF: KASAN: use-after-free Write in io_submit_one
>
> Tried to root-cause the issue, but need the patch submitter's help in
> coming up with a fix.
Hey George, thanks for the report. Do you have a reproducer?
One spot I don't like is how errors from bio_iov_iter_get_pages()
are handled, will test it.
diff --git a/block/fops.c b/block/fops.c
index ad732a36f9b3..211f44974d1e 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -342,7 +342,7 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
if (unlikely(ret)) {
bio->bi_status = BLK_STS_IOERR;
bio_endio(bio);
- return ret;
+ return -EIOCBQUEUED;
}
}
dio->size = bio->bi_iter.bi_size;
--
Pavel Begunkov
On 12/7/2021 12:36 PM, Pavel Begunkov wrote:
> On 12/7/21 15:51, George Kennedy wrote:
>> git bisect shows that commit 54a88eb838d3
>> ("block: add single bio async direct IO helper")
>> causes the following UAF: KASAN: use-after-free Write in io_submit_one
>>
>> Tried to root-cause the issue, but need the patch submitter's help in
>> coming up with a fix.
>
> Hey George, thanks for the report. Do you have a reproducer?
Hi Pavel,
Forgot to include it in the cover letter. Straight from Syzkaller:
#ifdef REF
Syzkaller hit 'KASAN: use-after-free Write in io_submit_one' bug.
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write
include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_sub_release
include/linux/atomic/atomic-instrumented.h:167 [inline]
BUG: KASAN: use-after-free in __refcount_sub_and_test
include/linux/refcount.h:272 [inline]
BUG: KASAN: use-after-free in __refcount_dec_and_test
include/linux/refcount.h:315 [inline]
BUG: KASAN: use-after-free in refcount_dec_and_test
include/linux/refcount.h:333 [inline]
BUG: KASAN: use-after-free in iocb_put fs/aio.c:1161 [inline]
BUG: KASAN: use-after-free in io_submit_one+0x496/0x2fe0 fs/aio.c:1882
Write of size 4 at addr ffff888027c338a0 by task syz-executor873/15100
CPU: 2 PID: 15100 Comm: syz-executor873 Not tainted 5.16.0-rc1-syzk #1
Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7860+a7792d29
04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106
print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold.14+0x7d/0x117 mm/kasan/report.c:450
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x18e/0x1f0 mm/kasan/generic.c:189
__kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_fetch_sub_release
include/linux/atomic/atomic-instrumented.h:167 [inline]
__refcount_sub_and_test include/linux/refcount.h:272 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
iocb_put fs/aio.c:1161 [inline]
io_submit_one+0x496/0x2fe0 fs/aio.c:1882
__do_sys_io_submit fs/aio.c:1938 [inline]
__se_sys_io_submit fs/aio.c:1908 [inline]
__x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f43c5504289
Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 8b 0d b7 db 2c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffda542ba68 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c5504289
RDX: 0000000020000400 RSI: 0000000000000001 RDI: 00007f43c5c14000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004006f0
R13: 00007ffda542bb50 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Allocated by task 15100:
kasan_save_stack+0x26/0x60 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
__kasan_slab_alloc+0x71/0x90 mm/kasan/common.c:467
kasan_slab_alloc include/linux/kasan.h:259 [inline]
slab_post_alloc_hook+0x55/0x230 mm/slab.h:519
slab_alloc_node mm/slub.c:3234 [inline]
slab_alloc mm/slub.c:3242 [inline]
kmem_cache_alloc+0x15a/0x2b0 mm/slub.c:3247
aio_get_req fs/aio.c:1028 [inline]
io_submit_one+0x122/0x2fe0 fs/aio.c:1875
__do_sys_io_submit fs/aio.c:1938 [inline]
__se_sys_io_submit fs/aio.c:1908 [inline]
__x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 15100:
kasan_save_stack+0x26/0x60 mm/kasan/common.c:38
kasan_set_track+0x25/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x24/0x40 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xe8/0x120 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook mm/slub.c:1749 [inline]
slab_free mm/slub.c:3513 [inline]
kmem_cache_free+0xfe/0x310 mm/slub.c:3530
iocb_destroy fs/aio.c:1080 [inline]
iocb_put fs/aio.c:1163 [inline]
iocb_put fs/aio.c:1159 [inline]
aio_complete_rw+0xa0f/0x1010 fs/aio.c:1440
aio_rw_done fs/aio.c:1510 [inline]
aio_read+0x352/0x4a0 fs/aio.c:1537
__io_submit_one fs/aio.c:1830 [inline]
io_submit_one+0x478/0x2fe0 fs/aio.c:1879
__do_sys_io_submit fs/aio.c:1938 [inline]
__se_sys_io_submit fs/aio.c:1908 [inline]
__x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
The buggy address belongs to the object at ffff888027c33800
which belongs to the cache aio_kiocb of size 176
The buggy address is located 160 bytes inside of
176-byte region [ffff888027c33800, ffff888027c338b0)
The buggy address belongs to the page:
page:00000000dfee8ade refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 pfn:0x27c33
flags: 0xfffffc0000200(slab|node=0|zone=1|lastcpupid=0x1fffff)
raw: 000fffffc0000200 ffffea0000714400 dead000000000002 ffff88810649da40
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888027c33780: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
ffff888027c33800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027c33880: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
^
ffff888027c33900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027c33980: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
==================================================================
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 2 PID: 15100 at lib/refcount.c:28
refcount_warn_saturate+0x111/0x200 lib/refcount.c:28
Modules linked in:
CPU: 2 PID: 15100 Comm: syz-executor873 Tainted: G B 5.16.0-rc1-syzk #1
Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7860+a7792d29
04/01/2014
RIP: 0010:refcount_warn_saturate+0x111/0x200 lib/refcount.c:28
Code: 1d fe 0e 02 11 31 ff 89 de e8 db 75 04 fe 84 db 75 9b e8 02 75 04
fe 48 c7 c7 60 57 53 8f c6 05 de 0e 02 11 01 e8 a8 32 7a 0a <0f> 0b e9
7c ff ff ff e8 e3 74 04 fe 0f b6 1d c4 0e 02 11 31 ff 89
RSP: 0018:ffff88801885fc90 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff816856a5
RDX: 0000000000000000 RSI: ffff888026f78000 RDI: 0000000000000002
RBP: ffff88801885fca0 R08: ffffed1020f27911 R09: ffffed1020f27911
R10: ffff88810793c887 R11: ffffed1020f27910 R12: ffff888027c338a0
R13: 0000000000000000 R14: ffff888027c33890 R15: 0000000000000000
FS: 00007f43c5c0d740(0000) GS:ffff888107900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f43c5c14000 CR3: 00000000247fe000 CR4: 00000000000006e0
Call Trace:
<TASK>
__refcount_sub_and_test include/linux/refcount.h:283 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
iocb_put fs/aio.c:1161 [inline]
io_submit_one+0xfd2/0x2fe0 fs/aio.c:1882
__do_sys_io_submit fs/aio.c:1938 [inline]
__se_sys_io_submit fs/aio.c:1908 [inline]
__x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f43c5504289
Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 8b 0d b7 db 2c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffda542ba68 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c5504289
RDX: 0000000020000400 RSI: 0000000000000001 RDI: 00007f43c5c14000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004006f0
R13: 00007ffda542bb50 R14: 0000000000000000 R15: 0000000000000000
</TASK>
---[ end trace 8c5b816eed9c8016 ]---
Syzkaller reproducer:
# {Threaded:false Collide:false Repeat:false RepeatTimes:0 Procs:1
Slowdown:1 Sandbox: Fault:false FaultCall:-1 FaultNth:0 Leak:false
NetInjection:false NetDevices:false NetReset:false Cgroups:false
BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false USB:false
VhciInjection:false Wifi:false IEEE802154:false Sysctl:false
UseTmpDir:false HandleSegv:false Repro:false Trace:false}
io_setup(0x3, &(0x7f0000000040)=<r0=>0x0)
r1 = openat$nullb(0xffffffffffffff9c, &(0x7f0000000000), 0x24080, 0x0)
io_submit(r0, 0x1, &(0x7f0000000400)=[&(0x7f0000000140)={0x0, 0x0, 0x0,
0x0, 0x0, r1, 0x0, 0xfe00}])
C reproducer:
#endif /* REF */
// autogenerated by syzkaller (https://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <endian.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
uint64_t r[2] = {0x0, 0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
intptr_t res = 0;
res = syscall(__NR_io_setup, 3, 0x20000040ul);
if (res != -1)
r[0] = *(uint64_t*)0x20000040;
memcpy((void*)0x20000000, "/dev/nullb0\000", 12);
res = syscall(__NR_openat, 0xffffffffffffff9cul, 0x20000000ul,
0x24080ul, 0ul);
if (res != -1)
r[1] = res;
*(uint64_t*)0x20000400 = 0x20000140;
*(uint64_t*)0x20000140 = 0;
*(uint32_t*)0x20000148 = 0;
*(uint32_t*)0x2000014c = 0;
*(uint16_t*)0x20000150 = 0;
*(uint16_t*)0x20000152 = 0;
*(uint32_t*)0x20000154 = r[1];
*(uint64_t*)0x20000158 = 0;
*(uint64_t*)0x20000160 = 0xfe00;
*(uint64_t*)0x20000168 = 0;
*(uint64_t*)0x20000170 = 0;
*(uint32_t*)0x20000178 = 0;
*(uint32_t*)0x2000017c = -1;
syscall(__NR_io_submit, r[0], 1ul, 0x20000400ul);
return 0;
}
Thanks,
George
>
> One spot I don't like is how errors from bio_iov_iter_get_pages()
> are handled, will test it.
>
> diff --git a/block/fops.c b/block/fops.c
> index ad732a36f9b3..211f44974d1e 100644
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -342,7 +342,7 @@ static ssize_t __blkdev_direct_IO_async(struct
> kiocb *iocb,
> if (unlikely(ret)) {
> bio->bi_status = BLK_STS_IOERR;
> bio_endio(bio);
> - return ret;
> + return -EIOCBQUEUED;
> }
> }
> dio->size = bio->bi_iter.bi_size;
>
>
On 12/7/21 18:09, George Kennedy wrote:
> On 12/7/2021 12:36 PM, Pavel Begunkov wrote:
>> On 12/7/21 15:51, George Kennedy wrote:
>>> git bisect shows that commit 54a88eb838d3
>>> ("block: add single bio async direct IO helper")
>>> causes the following UAF: KASAN: use-after-free Write in io_submit_one
>>>
>>> Tried to root-cause the issue, but need the patch submitter's help in
>>> coming up with a fix.
>>
>> Hey George, thanks for the report. Do you have a reproducer?
>
> Hi Pavel,
>
> Forgot to include it in the cover letter. Straight from Syzkaller:
Perfect, thanks! Confirmed what I thought about is a problem, though
the diff is buggy. Will take care of it
> #ifdef REF
> Syzkaller hit 'KASAN: use-after-free Write in io_submit_one' bug.
>
> ==================================================================
> BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> BUG: KASAN: use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:167 [inline]
> BUG: KASAN: use-after-free in __refcount_sub_and_test include/linux/refcount.h:272 [inline]
> BUG: KASAN: use-after-free in __refcount_dec_and_test include/linux/refcount.h:315 [inline]
> BUG: KASAN: use-after-free in refcount_dec_and_test include/linux/refcount.h:333 [inline]
> BUG: KASAN: use-after-free in iocb_put fs/aio.c:1161 [inline]
> BUG: KASAN: use-after-free in io_submit_one+0x496/0x2fe0 fs/aio.c:1882
> Write of size 4 at addr ffff888027c338a0 by task syz-executor873/15100
>
> CPU: 2 PID: 15100 Comm: syz-executor873 Not tainted 5.16.0-rc1-syzk #1
> Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7860+a7792d29 04/01/2014
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106
> print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247
> __kasan_report mm/kasan/report.c:433 [inline]
> kasan_report.cold.14+0x7d/0x117 mm/kasan/report.c:450
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x18e/0x1f0 mm/kasan/generic.c:189
> __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
> instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:167 [inline]
> __refcount_sub_and_test include/linux/refcount.h:272 [inline]
> __refcount_dec_and_test include/linux/refcount.h:315 [inline]
> refcount_dec_and_test include/linux/refcount.h:333 [inline]
> iocb_put fs/aio.c:1161 [inline]
> io_submit_one+0x496/0x2fe0 fs/aio.c:1882
> __do_sys_io_submit fs/aio.c:1938 [inline]
> __se_sys_io_submit fs/aio.c:1908 [inline]
> __x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f43c5504289
> Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d b7 db 2c 00 f7 d8 64 89 01 48
> RSP: 002b:00007ffda542ba68 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c5504289
> RDX: 0000000020000400 RSI: 0000000000000001 RDI: 00007f43c5c14000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004006f0
> R13: 00007ffda542bb50 R14: 0000000000000000 R15: 0000000000000000
> </TASK>
>
> Allocated by task 15100:
> kasan_save_stack+0x26/0x60 mm/kasan/common.c:38
> kasan_set_track mm/kasan/common.c:46 [inline]
> set_alloc_info mm/kasan/common.c:434 [inline]
> __kasan_slab_alloc+0x71/0x90 mm/kasan/common.c:467
> kasan_slab_alloc include/linux/kasan.h:259 [inline]
> slab_post_alloc_hook+0x55/0x230 mm/slab.h:519
> slab_alloc_node mm/slub.c:3234 [inline]
> slab_alloc mm/slub.c:3242 [inline]
> kmem_cache_alloc+0x15a/0x2b0 mm/slub.c:3247
> aio_get_req fs/aio.c:1028 [inline]
> io_submit_one+0x122/0x2fe0 fs/aio.c:1875
> __do_sys_io_submit fs/aio.c:1938 [inline]
> __se_sys_io_submit fs/aio.c:1908 [inline]
> __x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Freed by task 15100:
> kasan_save_stack+0x26/0x60 mm/kasan/common.c:38
> kasan_set_track+0x25/0x30 mm/kasan/common.c:46
> kasan_set_free_info+0x24/0x40 mm/kasan/generic.c:370
> ____kasan_slab_free mm/kasan/common.c:366 [inline]
> ____kasan_slab_free mm/kasan/common.c:328 [inline]
> __kasan_slab_free+0xe8/0x120 mm/kasan/common.c:374
> kasan_slab_free include/linux/kasan.h:235 [inline]
> slab_free_hook mm/slub.c:1723 [inline]
> slab_free_freelist_hook mm/slub.c:1749 [inline]
> slab_free mm/slub.c:3513 [inline]
> kmem_cache_free+0xfe/0x310 mm/slub.c:3530
> iocb_destroy fs/aio.c:1080 [inline]
> iocb_put fs/aio.c:1163 [inline]
> iocb_put fs/aio.c:1159 [inline]
> aio_complete_rw+0xa0f/0x1010 fs/aio.c:1440
> aio_rw_done fs/aio.c:1510 [inline]
> aio_read+0x352/0x4a0 fs/aio.c:1537
> __io_submit_one fs/aio.c:1830 [inline]
> io_submit_one+0x478/0x2fe0 fs/aio.c:1879
> __do_sys_io_submit fs/aio.c:1938 [inline]
> __se_sys_io_submit fs/aio.c:1908 [inline]
> __x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The buggy address belongs to the object at ffff888027c33800
> which belongs to the cache aio_kiocb of size 176
> The buggy address is located 160 bytes inside of
> 176-byte region [ffff888027c33800, ffff888027c338b0)
> The buggy address belongs to the page:
> page:00000000dfee8ade refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27c33
> flags: 0xfffffc0000200(slab|node=0|zone=1|lastcpupid=0x1fffff)
> raw: 000fffffc0000200 ffffea0000714400 dead000000000002 ffff88810649da40
> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff888027c33780: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
> ffff888027c33800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff888027c33880: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
> ^
> ffff888027c33900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888027c33980: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
> ==================================================================
> ------------[ cut here ]------------
> refcount_t: underflow; use-after-free.
> WARNING: CPU: 2 PID: 15100 at lib/refcount.c:28 refcount_warn_saturate+0x111/0x200 lib/refcount.c:28
> Modules linked in:
> CPU: 2 PID: 15100 Comm: syz-executor873 Tainted: G B 5.16.0-rc1-syzk #1
> Hardware name: Red Hat KVM, BIOS 1.13.0-2.module+el8.3.0+7860+a7792d29 04/01/2014
> RIP: 0010:refcount_warn_saturate+0x111/0x200 lib/refcount.c:28
> Code: 1d fe 0e 02 11 31 ff 89 de e8 db 75 04 fe 84 db 75 9b e8 02 75 04 fe 48 c7 c7 60 57 53 8f c6 05 de 0e 02 11 01 e8 a8 32 7a 0a <0f> 0b e9 7c ff ff ff e8 e3 74 04 fe 0f b6 1d c4 0e 02 11 31 ff 89
> RSP: 0018:ffff88801885fc90 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff816856a5
> RDX: 0000000000000000 RSI: ffff888026f78000 RDI: 0000000000000002
> RBP: ffff88801885fca0 R08: ffffed1020f27911 R09: ffffed1020f27911
> R10: ffff88810793c887 R11: ffffed1020f27910 R12: ffff888027c338a0
> R13: 0000000000000000 R14: ffff888027c33890 R15: 0000000000000000
> FS: 00007f43c5c0d740(0000) GS:ffff888107900000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f43c5c14000 CR3: 00000000247fe000 CR4: 00000000000006e0
> Call Trace:
> <TASK>
> __refcount_sub_and_test include/linux/refcount.h:283 [inline]
> __refcount_dec_and_test include/linux/refcount.h:315 [inline]
> refcount_dec_and_test include/linux/refcount.h:333 [inline]
> iocb_put fs/aio.c:1161 [inline]
> io_submit_one+0xfd2/0x2fe0 fs/aio.c:1882
> __do_sys_io_submit fs/aio.c:1938 [inline]
> __se_sys_io_submit fs/aio.c:1908 [inline]
> __x64_sys_io_submit+0x1c7/0x4a0 fs/aio.c:1908
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f43c5504289
> Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d b7 db 2c 00 f7 d8 64 89 01 48
> RSP: 002b:00007ffda542ba68 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c5504289
> RDX: 0000000020000400 RSI: 0000000000000001 RDI: 00007f43c5c14000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004006f0
> R13: 00007ffda542bb50 R14: 0000000000000000 R15: 0000000000000000
> </TASK>
> ---[ end trace 8c5b816eed9c8016 ]---
>
>
> Syzkaller reproducer:
> # {Threaded:false Collide:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: Fault:false FaultCall:-1 FaultNth:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:false UseTmpDir:false HandleSegv:false Repro:false Trace:false}
> io_setup(0x3, &(0x7f0000000040)=<r0=>0x0)
> r1 = openat$nullb(0xffffffffffffff9c, &(0x7f0000000000), 0x24080, 0x0)
> io_submit(r0, 0x1, &(0x7f0000000400)=[&(0x7f0000000140)={0x0, 0x0, 0x0, 0x0, 0x0, r1, 0x0, 0xfe00}])
>
>
> C reproducer:
> #endif /* REF */
> // autogenerated by syzkaller (https://github.com/google/syzkaller)
>
> #define _GNU_SOURCE
>
> #include <endian.h>
> #include <stdint.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/syscall.h>
> #include <sys/types.h>
> #include <unistd.h>
>
> uint64_t r[2] = {0x0, 0xffffffffffffffff};
>
> int main(void)
> {
> syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
> syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
> syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
> intptr_t res = 0;
> res = syscall(__NR_io_setup, 3, 0x20000040ul);
> if (res != -1)
> r[0] = *(uint64_t*)0x20000040;
> memcpy((void*)0x20000000, "/dev/nullb0\000", 12);
> res = syscall(__NR_openat, 0xffffffffffffff9cul, 0x20000000ul, 0x24080ul, 0ul);
> if (res != -1)
> r[1] = res;
> *(uint64_t*)0x20000400 = 0x20000140;
> *(uint64_t*)0x20000140 = 0;
> *(uint32_t*)0x20000148 = 0;
> *(uint32_t*)0x2000014c = 0;
> *(uint16_t*)0x20000150 = 0;
> *(uint16_t*)0x20000152 = 0;
> *(uint32_t*)0x20000154 = r[1];
> *(uint64_t*)0x20000158 = 0;
> *(uint64_t*)0x20000160 = 0xfe00;
> *(uint64_t*)0x20000168 = 0;
> *(uint64_t*)0x20000170 = 0;
> *(uint32_t*)0x20000178 = 0;
> *(uint32_t*)0x2000017c = -1;
> syscall(__NR_io_submit, r[0], 1ul, 0x20000400ul);
> return 0;
> }
>
> Thanks,
> George
>>
>> One spot I don't like is how errors from bio_iov_iter_get_pages()
>> are handled, will test it.
>>
>> diff --git a/block/fops.c b/block/fops.c
>> index ad732a36f9b3..211f44974d1e 100644
>> --- a/block/fops.c
>> +++ b/block/fops.c
>> @@ -342,7 +342,7 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
>> if (unlikely(ret)) {
>> bio->bi_status = BLK_STS_IOERR;
>> bio_endio(bio);
>> - return ret;
>> + return -EIOCBQUEUED;
>> }
>> }
>> dio->size = bio->bi_iter.bi_size;
>>
>>
>
--
Pavel Begunkov