| From b21e1a91e13abaff3731c15b0cccbe392cff9e2a Mon Sep 17 00:00:00 2001 |
| From: Qian Cai <cai@lca.pw> |
| Date: Fri, 21 Feb 2020 23:32:58 -0500 |
| Subject: [PATCH] ext4: fix a data race at inode->i_blocks |
| |
| commit 28936b62e71e41600bab319f262ea9f9b1027629 upstream. |
| |
| inode->i_blocks could be accessed concurrently as noticed by KCSAN, |
| |
| BUG: KCSAN: data-race in ext4_do_update_inode [ext4] / inode_add_bytes |
| |
| write to 0xffff9a00d4b982d0 of 8 bytes by task 22100 on cpu 118: |
| inode_add_bytes+0x65/0xf0 |
| __inode_add_bytes at fs/stat.c:689 |
| (inlined by) inode_add_bytes at fs/stat.c:702 |
| ext4_mb_new_blocks+0x418/0xca0 [ext4] |
| ext4_ext_map_blocks+0x1a6b/0x27b0 [ext4] |
| ext4_map_blocks+0x1a9/0x950 [ext4] |
| _ext4_get_block+0xfc/0x270 [ext4] |
| ext4_get_block_unwritten+0x33/0x50 [ext4] |
| __block_write_begin_int+0x22e/0xae0 |
| __block_write_begin+0x39/0x50 |
| ext4_write_begin+0x388/0xb50 [ext4] |
| ext4_da_write_begin+0x35f/0x8f0 [ext4] |
| generic_perform_write+0x15d/0x290 |
| ext4_buffered_write_iter+0x11f/0x210 [ext4] |
| ext4_file_write_iter+0xce/0x9e0 [ext4] |
| new_sync_write+0x29c/0x3b0 |
| __vfs_write+0x92/0xa0 |
| vfs_write+0x103/0x260 |
| ksys_write+0x9d/0x130 |
| __x64_sys_write+0x4c/0x60 |
| do_syscall_64+0x91/0xb05 |
| entry_SYSCALL_64_after_hwframe+0x49/0xbe |
| |
| read to 0xffff9a00d4b982d0 of 8 bytes by task 8 on cpu 65: |
| ext4_do_update_inode+0x4a0/0xf60 [ext4] |
| ext4_inode_blocks_set at fs/ext4/inode.c:4815 |
| ext4_mark_iloc_dirty+0xaf/0x160 [ext4] |
| ext4_mark_inode_dirty+0x129/0x3e0 [ext4] |
| ext4_convert_unwritten_extents+0x253/0x2d0 [ext4] |
| ext4_convert_unwritten_io_end_vec+0xc5/0x150 [ext4] |
| ext4_end_io_rsv_work+0x22c/0x350 [ext4] |
| process_one_work+0x54f/0xb90 |
| worker_thread+0x80/0x5f0 |
| kthread+0x1cd/0x1f0 |
| ret_from_fork+0x27/0x50 |
| |
| 4 locks held by kworker/u256:0/8: |
| #0: ffff9a025abc4328 ((wq_completion)ext4-rsv-conversion){+.+.}, at: process_one_work+0x443/0xb90 |
| #1: ffffab5a862dbe20 ((work_completion)(&ei->i_rsv_conversion_work)){+.+.}, at: process_one_work+0x443/0xb90 |
| #2: ffff9a025a9d0f58 (jbd2_handle){++++}, at: start_this_handle+0x1c1/0x9d0 [jbd2] |
| #3: ffff9a00d4b985d8 (&(&ei->i_raw_lock)->rlock){+.+.}, at: ext4_do_update_inode+0xaa/0xf60 [ext4] |
| irq event stamp: 3009267 |
| hardirqs last enabled at (3009267): [<ffffffff980da9b7>] __find_get_block+0x107/0x790 |
| hardirqs last disabled at (3009266): [<ffffffff980da8f9>] __find_get_block+0x49/0x790 |
| softirqs last enabled at (3009230): [<ffffffff98a0034c>] __do_softirq+0x34c/0x57c |
| softirqs last disabled at (3009223): [<ffffffff97cc67a2>] irq_exit+0xa2/0xc0 |
| |
| Reported by Kernel Concurrency Sanitizer on: |
| CPU: 65 PID: 8 Comm: kworker/u256:0 Tainted: G L 5.6.0-rc2-next-20200221+ #7 |
| Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 |
| Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work [ext4] |
| |
| The plain read is outside of inode->i_lock critical section which |
| results in a data race. Fix it by adding READ_ONCE() there. |
| |
| Link: https://lore.kernel.org/r/20200222043258.2279-1-cai@lca.pw |
| Signed-off-by: Qian Cai <cai@lca.pw> |
| Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
| Cc: stable@kernel.org |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c |
| index ac4d3c9fbd79..d863ef29e030 100644 |
| --- a/fs/ext4/inode.c |
| +++ b/fs/ext4/inode.c |
| @@ -5168,7 +5168,7 @@ static int ext4_inode_blocks_set(handle_t *handle, |
| struct ext4_inode_info *ei) |
| { |
| struct inode *inode = &(ei->vfs_inode); |
| - u64 i_blocks = inode->i_blocks; |
| + u64 i_blocks = READ_ONCE(inode->i_blocks); |
| struct super_block *sb = inode->i_sb; |
| |
| if (i_blocks <= ~0U) { |
| -- |
| 2.7.4 |
| |