在 2022/7/19 19:26, Greg KH 写道:
On Sat, Jul 16, 2022 at 10:33:30AM +0800, Baokun Li wrote:
在 2022/7/15 22:10, Greg KH 写道:
On Fri, Jul 15, 2022 at 10:39:28AM +0800, Baokun Li wrote:
This patch and problem analysis is based on v4.19 LTS. The d3b6f23f7167("ext4: move ext4_fiemap to use iomap framework") patch is incorporated in v5.7-rc1. This patch avoids this problem by switching to iomap in ext4_fiemap.
Hulk Robot reported a BUG on stable 4.19.252:
kernel BUG at fs/ext4/extents_status.c:762! invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 7 PID: 2845 Comm: syz-executor Not tainted 4.19.252 #46 RIP: 0010:ext4_es_cache_extent+0x30e/0x370 [...] Call Trace: ext4_cache_extents+0x238/0x2f0 ext4_find_extent+0x785/0xa40 ext4_fiemap+0x36d/0xe90 do_vfs_ioctl+0x6af/0x1200 [...] ==================================================================
Above issue may happen as follows:
cpu1 cpu2_____________________|_____________________ do_vfs_ioctl ext4_ioctl ext4_ioctl_setflags ext4_ind_migrate do_vfs_ioctl ioctl_fiemap ext4_fiemap ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) ext4_fill_fiemap_extents down_write(&EXT4_I(inode)->i_data_sem); ext4_ext_check_inode ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS) memset(ei->i_data, 0, sizeof(ei->i_data)) up_write(&EXT4_I(inode)->i_data_sem); down_read(&EXT4_I(inode)->i_data_sem); ext4_find_extent ext4_cache_extents ext4_es_cache_extent BUG_ON(end < lblk)
We can easily reproduce this problem with the syzkaller testcase:
02:37:07 executing program 3: r0 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\x00', 0x26e1, 0x0) ioctl$FS_IOC_FSSETXATTR(r0, 0x40086602, &(0x7f0000000080)={0x17e}) mkdirat(0xffffffffffffff9c, &(0x7f00000000c0)='./file1\x00', 0x1ff) r1 = openat(0xffffffffffffff9c, &(0x7f0000000100)='./file1\x00', 0x0, 0x0) ioctl$FS_IOC_FIEMAP(r1, 0xc020660b, &(0x7f0000000180)={0x0, 0x1, 0x0, 0xef3, 0x6, []}) (async, rerun: 32) ioctl$FS_IOC_FSSETXATTR(r1, 0x40086602, &(0x7f0000000140)={0x17e}) (rerun: 32)To solve this issue, we use __generic_block_fiemap() instead of generic_block_fiemap() and add inode_lock_shared to avoid race condition.
Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Baokun Li libaokun1@huawei.com
fs/ext4/extents.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
What is the git commit id of this change in Linus's tree?
If it is not in Linus's tree, why not?
confused,
greg k-h .
This patch does not exist in the Linus' tree.
This problem persists until the patch d3b6f23f7167("ext4: move ext4_fiemap to use iomap framework") is incorporated in v5.7-rc1.
Then why not ask for that change to be added instead?
thanks,
greg k-h .
If we want to switch to the iomap framework, we need to analyze and integrate about 60 patches.
The workload may be greater than that of solving this problem alone.
Thank you!
Thanks a lot!