| From 39b77aa67201df647c34cd59d219c296bfd0d2ef Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 11 Aug 2025 22:18:30 +0800 |
| Subject: fs/buffer: fix use-after-free when call bh_read() helper |
| |
| From: Ye Bin <yebin10@huawei.com> |
| |
| [ Upstream commit 7375f22495e7cd1c5b3b5af9dcc4f6dffe34ce49 ] |
| |
| There's issue as follows: |
| BUG: KASAN: stack-out-of-bounds in end_buffer_read_sync+0xe3/0x110 |
| Read of size 8 at addr ffffc9000168f7f8 by task swapper/3/0 |
| CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted 6.16.0-862.14.0.6.x86_64 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) |
| Call Trace: |
| <IRQ> |
| dump_stack_lvl+0x55/0x70 |
| print_address_description.constprop.0+0x2c/0x390 |
| print_report+0xb4/0x270 |
| kasan_report+0xb8/0xf0 |
| end_buffer_read_sync+0xe3/0x110 |
| end_bio_bh_io_sync+0x56/0x80 |
| blk_update_request+0x30a/0x720 |
| scsi_end_request+0x51/0x2b0 |
| scsi_io_completion+0xe3/0x480 |
| ? scsi_device_unbusy+0x11e/0x160 |
| blk_complete_reqs+0x7b/0x90 |
| handle_softirqs+0xef/0x370 |
| irq_exit_rcu+0xa5/0xd0 |
| sysvec_apic_timer_interrupt+0x6e/0x90 |
| </IRQ> |
| |
| Above issue happens when do ntfs3 filesystem mount, issue may happens |
| as follows: |
| mount IRQ |
| ntfs_fill_super |
| read_cache_page |
| do_read_cache_folio |
| filemap_read_folio |
| mpage_read_folio |
| do_mpage_readpage |
| ntfs_get_block_vbo |
| bh_read |
| submit_bh |
| wait_on_buffer(bh); |
| blk_complete_reqs |
| scsi_io_completion |
| scsi_end_request |
| blk_update_request |
| end_bio_bh_io_sync |
| end_buffer_read_sync |
| __end_buffer_read_notouch |
| unlock_buffer |
| |
| wait_on_buffer(bh);--> return will return to caller |
| |
| put_bh |
| --> trigger stack-out-of-bounds |
| In the mpage_read_folio() function, the stack variable 'map_bh' is |
| passed to ntfs_get_block_vbo(). Once unlock_buffer() unlocks and |
| wait_on_buffer() returns to continue processing, the stack variable |
| is likely to be reclaimed. Consequently, during the end_buffer_read_sync() |
| process, calling put_bh() may result in stack overrun. |
| |
| If the bh is not allocated on the stack, it belongs to a folio. Freeing |
| a buffer head which belongs to a folio is done by drop_buffers() which |
| will fail to free buffers which are still locked. So it is safe to call |
| put_bh() before __end_buffer_read_notouch(). |
| |
| Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") |
| Signed-off-by: Ye Bin <yebin10@huawei.com> |
| Link: https://lore.kernel.org/20250811141830.343774-1-yebin@huaweicloud.com |
| Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> |
| Signed-off-by: Christian Brauner <brauner@kernel.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| fs/buffer.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/fs/buffer.c b/fs/buffer.c |
| index d9c6d1fbb6dd..3033a937e3a5 100644 |
| --- a/fs/buffer.c |
| +++ b/fs/buffer.c |
| @@ -156,8 +156,8 @@ static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
| */ |
| void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
| { |
| - __end_buffer_read_notouch(bh, uptodate); |
| put_bh(bh); |
| + __end_buffer_read_notouch(bh, uptodate); |
| } |
| EXPORT_SYMBOL(end_buffer_read_sync); |
| |
| -- |
| 2.50.1 |
| |
