In the Linux kernel, the following vulnerability has been resolved:

ext4: fix use-after-free in ext4_orphan_cleanup

I caught a issue as follows:

BUG: KASAN: use-after-free in __list_add_valid+0x28/0x1a0 Read of size 8 at addr ffff88814b13f378 by task mount/710

CPU: 1 PID: 710 Comm: mount Not tainted 6.1.0-rc3-next #370 Call Trace: dump_stack_lvl+0x73/0x9f print_report+0x25d/0x759 kasan_report+0xc0/0x120 __asan_load8+0x99/0x140 __list_add_valid+0x28/0x1a0 ext4_orphan_cleanup+0x564/0x9d0 [ext4] __ext4_fill_super+0x48e2/0x5300 [ext4] ext4_fill_super+0x19f/0x3a0 [ext4] get_tree_bdev+0x27b/0x450 ext4_get_tree+0x19/0x30 [ext4] vfs_get_tree+0x49/0x150 path_mount+0xaae/0x1350 do_mount+0xe2/0x110 __x64_sys_mount+0xf0/0x190 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd […]

Above issue may happen as follows:

ext4_fill_super ext4_orphan_cleanup — loop1: assume last_orphan is 12 — list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan) ext4_truncate –> return 0 ext4_inode_attach_jinode –> return -ENOMEM iput(inode) –> free inode<12> — loop2: last_orphan is still 12 — list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan); // use inode<12> and trigger UAF

To solve this issue, we need to propagate the return value of ext4_inode_attach_jinode() appropriately.

Affected Software

References

• https://git.kernel.org/stable/c/026a4490b5381229a30f23d073b58e8e35ee6858
• https://git.kernel.org/stable/c/7223d5e75f26352354ea2c0ccf8b579821b52adf
• https://git.kernel.org/stable/c/7908b8a541b1578cc61b4da7f19b604a931441da
• https://git.kernel.org/stable/c/7f801a1593cb957f73659732836b2dafbdfc7709
• https://git.kernel.org/stable/c/a71248b1accb2b42e4980afef4fa4a27fa0e36f5
• https://git.kernel.org/stable/c/c2bdbd4c69308835d1b6f6ba74feeccbfe113478
• https://git.kernel.org/stable/c/cf0e0817b0f925b70d101d7014ea81b7094e1159