[PATCH AUTOSEL 5.4 21/23] block: reexpand iov_iter after read/write

Sasha Levin
2021-05-12T19:57:40Z

From: yangerkun <yangerkun@huawei.com>

[ Upstream commit cf7b39a0cbf6bf57aa07a008d46cf695add05b4c ]

We get a bug:

BUG: KASAN: slab-out-of-bounds in iov_iter_revert+0x11c/0x404
lib/iov_iter.c:1139
Read of size 8 at addr ffff0000d3fb11f8 by task

CPU: 0 PID: 12582 Comm: syz-executor.2 Not tainted
5.10.0-00843-g352c8610ccd2 #2
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x0/0x2d0 arch/arm64/kernel/stacktrace.c:132
show_stack+0x28/0x34 arch/arm64/kernel/stacktrace.c:196
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x110/0x164 lib/dump_stack.c:118
print_address_description+0x78/0x5c8 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report+0x148/0x1e4 mm/kasan/report.c:562
check_memory_region_inline mm/kasan/generic.c:183 [inline]
__asan_load8+0xb4/0xbc mm/kasan/generic.c:252
iov_iter_revert+0x11c/0x404 lib/iov_iter.c:1139
io_read fs/io_uring.c:3421 [inline]
io_issue_sqe+0x2344/0x2d64 fs/io_uring.c:5943
__io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
io_submit_sqe fs/io_uring.c:6395 [inline]
io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
__do_sys_io_uring_enter fs/io_uring.c:9013 [inline]
__se_sys_io_uring_enter fs/io_uring.c:8960 [inline]
__arm64_sys_io_uring_enter+0x190/0x708 fs/io_uring.c:8960
__invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:227
el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

Allocated by task 12570:
stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0xdc/0x120 mm/kasan/common.c:461
kasan_kmalloc+0xc/0x14 mm/kasan/common.c:475
__kmalloc+0x23c/0x334 mm/slub.c:3970
kmalloc include/linux/slab.h:557 [inline]
__io_alloc_async_data+0x68/0x9c fs/io_uring.c:3210
io_setup_async_rw fs/io_uring.c:3229 [inline]
io_read fs/io_uring.c:3436 [inline]
io_issue_sqe+0x2954/0x2d64 fs/io_uring.c:5943
__io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
io_submit_sqe fs/io_uring.c:6395 [inline]
io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
__do_sys_io_uring_enter fs/io_uring.c:9013 [inline]
__se_sys_io_uring_enter fs/io_uring.c:8960 [inline]
__arm64_sys_io_uring_enter+0x190/0x708 fs/io_uring.c:8960
__invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:227
el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

Freed by task 12570:
stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
kasan_save_stack mm/kasan/common.c:48 [inline]
kasan_set_track+0x38/0x6c mm/kasan/common.c:56
kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:355
__kasan_slab_free+0x124/0x150 mm/kasan/common.c:422
kasan_slab_free+0x10/0x1c mm/kasan/common.c:431
slab_free_hook mm/slub.c:1544 [inline]
slab_free_freelist_hook mm/slub.c:1577 [inline]
slab_free mm/slub.c:3142 [inline]
kfree+0x104/0x38c mm/slub.c:4124
io_dismantle_req fs/io_uring.c:1855 [inline]
__io_free_req+0x70/0x254 fs/io_uring.c:1867
io_put_req_find_next fs/io_uring.c:2173 [inline]
__io_queue_sqe+0x1fc/0x520 fs/io_uring.c:6279
__io_req_task_submit+0x154/0x21c fs/io_uring.c:2051
io_req_task_submit+0x2c/0x44 fs/io_uring.c:2063
task_work_run+0xdc/0x128 kernel/task_work.c:151
get_signal+0x6f8/0x980 kernel/signal.c:2562
do_signal+0x108/0x3a4 arch/arm64/kernel/signal.c:658
do_notify_resume+0xbc/0x25c arch/arm64/kernel/signal.c:722
work_pending+0xc/0x180

blkdev_read_iter can truncate iov_iter's count since the count + pos may
exceed the size of the blkdev. This will confuse io_read that we have
consume the iovec. And once we do the iov_iter_revert in io_read, we
will trigger the slab-out-of-bounds. Fix it by reexpand the count with
size has been truncated.

blkdev_write_iter can trigger the problem too.

Signed-off-by: yangerkun <yangerkun@huawei.com>
Acked-by: Pavel Begunkov <asml.silencec@gmail.com>
Link: https://lore.kernel.org/r/20210401071807.3328235-1-yangerkun@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/block_dev.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index bd93563477a4..fa329c7eddf0 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1987,6 +1987,7 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
struct inode *bd_inode = bdev_file_inode(file);
loff_t size = i_size_read(bd_inode);
struct blk_plug plug;
+ size_t shorted = 0;
ssize_t ret;

if (bdev_read_only(I_BDEV(bd_inode)))
@@ -2005,12 +2006,17 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
return -EOPNOTSUPP;

- iov_iter_truncate(from, size - iocb->ki_pos);
+ size -= iocb->ki_pos;
+ if (iov_iter_count(from) > size) {
+ shorted = iov_iter_count(from) - size;
+ iov_iter_truncate(from, size);
+ }

blk_start_plug(&plug);
ret = __generic_file_write_iter(iocb, from);
if (ret > 0)
ret = generic_write_sync(iocb, ret);
+ iov_iter_reexpand(from, iov_iter_count(from) + shorted);
blk_finish_plug(&plug);
return ret;
}
@@ -2022,13 +2028,21 @@ ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
struct inode *bd_inode = bdev_file_inode(file);
loff_t size = i_size_read(bd_inode);
loff_t pos = iocb->ki_pos;
+ size_t shorted = 0;
+ ssize_t ret;

if (pos >= size)
return 0;

size -= pos;
- iov_iter_truncate(to, size);
- return generic_file_read_iter(iocb, to);
+ if (iov_iter_count(to) > size) {
+ shorted = iov_iter_count(to) - size;
+ iov_iter_truncate(to, size);
+ }
+
+ ret = generic_file_read_iter(iocb, to);
+ iov_iter_reexpand(to, iov_iter_count(to) + shorted);
+ return ret;
}
EXPORT_SYMBOL_GPL(blkdev_read_iter);

--
2.30.2