6.10-stable review patch. If anyone has any objections, please let me know.
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From: Ofir Gal ofir.gal@volumez.com
commit ab99a87542f194f28e2364a42afbf9fb48b1c724 upstream.
__write_sb_page() rounds up the io size to the optimal io size if it doesn't exceed the data offset, but it doesn't check the final size exceeds the bitmap length.
For example: page count - 1 page size - 4K data offset - 1M optimal io size - 256K
The final io size would be 256K (64 pages) but md_bitmap_storage_alloc() allocated 1 page, the IO would write 1 valid page and 63 pages that happens to be allocated afterwards. This leaks memory to the raid device superblock.
This issue caused a data transfer failure in nvme-tcp. The network drivers checks the first page of an IO with sendpage_ok(), it returns true if the page isn't a slabpage and refcount >= 1. If the page !sendpage_ok() the network driver disables MSG_SPLICE_PAGES.
As of now the network layer assumes all the pages of the IO are sendpage_ok() when MSG_SPLICE_PAGES is on.
The bitmap pages aren't slab pages, the first page of the IO is sendpage_ok(), but the additional pages that happens to be allocated after the bitmap pages might be !sendpage_ok(). That cause skb_splice_from_iter() to stop the data transfer, in the case below it hangs 'mdadm --create'.
The bug is reproducible, in order to reproduce we need nvme-over-tcp controllers with optimal IO size bigger than PAGE_SIZE. Creating a raid with bitmap over those devices reproduces the bug.
In order to simulate large optimal IO size you can use dm-stripe with a single device. Script to reproduce the issue on top of brd devices using dm-stripe is attached below (will be added to blktest).
I have added some logs to test the theory: ... md: created bitmap (1 pages) for device md127 __write_sb_page before md_super_write offset: 16, size: 262144. pfn: 0x53ee === __write_sb_page before md_super_write. logging pages === pfn: 0x53ee, slab: 0 <-- the only page that allocated for the bitmap pfn: 0x53ef, slab: 1 pfn: 0x53f0, slab: 0 pfn: 0x53f1, slab: 0 pfn: 0x53f2, slab: 0 pfn: 0x53f3, slab: 1 ... nvme_tcp: sendpage_ok - pfn: 0x53ee, len: 262144, offset: 0 skbuff: before sendpage_ok() - pfn: 0x53ee skbuff: before sendpage_ok() - pfn: 0x53ef WARNING at net/core/skbuff.c:6848 skb_splice_from_iter+0x142/0x450 skbuff: !sendpage_ok - pfn: 0x53ef. is_slab: 1, page_count: 1 ...
Cc: stable@vger.kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Ofir Gal ofir.gal@volumez.com Signed-off-by: Song Liu song@kernel.org Link: https://lore.kernel.org/r/20240607072748.3182199-1-ofir.gal@volumez.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/md-bitmap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/md/md-bitmap.c +++ b/drivers/md/md-bitmap.c @@ -227,6 +227,8 @@ static int __write_sb_page(struct md_rde struct block_device *bdev; struct mddev *mddev = bitmap->mddev; struct bitmap_storage *store = &bitmap->storage; + unsigned int bitmap_limit = (bitmap->storage.file_pages - pg_index) << + PAGE_SHIFT; loff_t sboff, offset = mddev->bitmap_info.offset; sector_t ps = pg_index * PAGE_SIZE / SECTOR_SIZE; unsigned int size = PAGE_SIZE; @@ -269,11 +271,9 @@ static int __write_sb_page(struct md_rde if (size == 0) /* bitmap runs in to data */ return -EINVAL; - } else { - /* DATA METADATA BITMAP - no problems */ }
- md_super_write(mddev, rdev, sboff + ps, (int) size, page); + md_super_write(mddev, rdev, sboff + ps, (int)min(size, bitmap_limit), page); return 0; }