published July 10, 2025
In the Linux kernel, the following vulnerability has been resolved:
jbd2: fix data-race and null-ptr-deref in jbd2_journal_dirty_metadata()
Since handle->h_transaction may be a NULL pointer, so we should change it
to call is_handle_aborted(handle) first before dereferencing it.
And the following data-race was reported in my fuzzer:
==================================================================
BUG: KCSAN: data-race in jbd2_journal_dirty_metadata / jbd2_journal_dirty_metadata
write to 0xffff888011024104 of 4 bytes by task 10881 on cpu 1:
jbd2_journal_dirty_metadata+0x2a5/0x770 fs/jbd2/transaction.c:1556
__ext4_handle_dirty_metadata+0xe7/0x4b0 fs/ext4/ext4_jbd2.c:358
ext4_do_update_inode fs/ext4/inode.c:5220 [inline]
ext4_mark_iloc_dirty+0x32c/0xd50 fs/ext4/inode.c:5869
__ext4_mark_inode_dirty+0xe1/0x450 fs/ext4/inode.c:6074
ext4_dirty_inode+0x98/0xc0 fs/ext4/inode.c:6103
....
read to 0xffff888011024104 of 4 bytes by task 10880 on cpu 0:
jbd2_journal_dirty_metadata+0xf2/0x770 fs/jbd2/transaction.c:1512
__ext4_handle_dirty_metadata+0xe7/0x4b0 fs/ext4/ext4_jbd2.c:358
ext4_do_update_inode fs/ext4/inode.c:5220 [inline]
ext4_mark_iloc_dirty+0x32c/0xd50 fs/ext4/inode.c:5869
__ext4_mark_inode_dirty+0xe1/0x450 fs/ext4/inode.c:6074
ext4_dirty_inode+0x98/0xc0 fs/ext4/inode.c:6103
....
value changed: 0x00000000 -> 0x00000001
==================================================================
This issue is caused by missing data-race annotation for jh->b_modified.
Therefore, the missing annotation needs to be added.