bio_max_size() may get called before device_add_disk() and hence needs to
check whether or not the block device pointer is NULL. Additionally, more
code needs to be modified than __bio_try_merge_page() to limit the bio size
to bio_max_size().
This patch prevents that bio_max_size() triggers the following kernel
crash during a SCSI LUN scan:
BUG: KASAN: null-ptr-deref in bio_add_hw_page+0xa6/0x310
Read of size 8 at addr 00000000000005a8 by task kworker/u16:0/7
Workqueue: events_unbound async_run_entry_fn
Call Trace:
show_stack+0x52/0x58
dump_stack+0x9d/0xcf
kasan_report.cold+0x4b/0x50
__asan_load8+0x69/0x90
bio_add_hw_page+0xa6/0x310
bio_add_pc_page+0xaa/0xe0
bio_map_kern+0xdc/0x1a0
blk_rq_map_kern+0xcd/0x2d0
__scsi_execute+0x9a/0x290 [scsi_mod]
scsi_probe_lun.constprop.0+0x17c/0x660 [scsi_mod]
scsi_probe_and_add_lun+0x178/0x750 [scsi_mod]
__scsi_add_device+0x18c/0x1a0 [scsi_mod]
ata_scsi_scan_host+0xe5/0x260 [libata]
async_port_probe+0x94/0xb0 [libata]
async_run_entry_fn+0x7d/0x2d0
process_one_work+0x582/0xac0
worker_thread+0x8f/0x5a0
kthread+0x222/0x250
ret_from_fork+0x1f/0x30
This patch also fixes the following kernel warning:
WARNING: CPU: 1 PID: 15449 at block/bio.c:1034
__bio_iov_iter_get_pages+0x324/0x350
Call Trace:
bio_iov_iter_get_pages+0x6c/0x360
__blkdev_direct_IO_simple+0x291/0x580
blkdev_direct_IO+0xb5/0xc0
generic_file_direct_write+0x10d/0x290
__generic_file_write_iter+0x120/0x290
blkdev_write_iter+0x16e/0x280
new_sync_write+0x268/0x380
vfs_write+0x3e0/0x4f0
ksys_write+0xd9/0x180
__x64_sys_write+0x43/0x50
do_syscall_64+0x32/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Changheun Lee <nanich.lee@xxxxxxxxxxx>
Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Fixes: 15050b63567c ("bio: limit bio max size")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/bio.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
Changes compared to v1: included a fix for direct I/O.
diff --git a/block/bio.c b/block/bio.c
index d718c63b3533..221dc56ba22f 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -257,9 +257,9 @@ EXPORT_SYMBOL(bio_init);
unsigned int bio_max_size(struct bio *bio)
{
- struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+ struct block_device *bdev = bio->bi_bdev;
- return q->limits.bio_max_bytes;
+ return bdev ? bdev->bd_disk->queue->limits.bio_max_bytes : UINT_MAX;
}
/**
@@ -1002,6 +1002,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
{
unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
+ unsigned int bytes_left = bio_max_size(bio) - bio->bi_iter.bi_size;
struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
struct page **pages = (struct page **)bv;
bool same_page = false;
@@ -1017,7 +1018,8 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
- size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
+ size = iov_iter_get_pages(iter, pages, bytes_left, nr_pages,
+ &offset);
if (unlikely(size <= 0))
return size ? size : -EFAULT;
