CVE-2022-49349

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

ext4: fix use-after-free in ext4_rename_dir_prepare

We got issue as follows:

EXT4-fs (loop0): mounted filesystem without journal. Opts: ,errors=continue

ext4_get_first_dir_block: bh->b_data=0xffff88810bee6000 len=34478

ext4_get_first_dir_block: *parent_de=0xffff88810beee6ae bh->b_data=0xffff88810bee6000

ext4_rename_dir_prepare: [1] parent_de=0xffff88810beee6ae

==================================================================

BUG: KASAN: use-after-free in ext4_rename_dir_prepare+0x152/0x220

Read of size 4 at addr ffff88810beee6ae by task rep/1895

CPU: 13 PID: 1895 Comm: rep Not tainted 5.10.0+ #241

Call Trace:

dump_stack+0xbe/0xf9

print_address_description.constprop.0+0x1e/0x220

kasan_report.cold+0x37/0x7f

ext4_rename_dir_prepare+0x152/0x220

ext4_rename+0xf44/0x1ad0

ext4_rename2+0x11c/0x170

vfs_rename+0xa84/0x1440

do_renameat2+0x683/0x8f0

__x64_sys_renameat+0x53/0x60

do_syscall_64+0x33/0x40

entry_SYSCALL_64_after_hwframe+0x44/0xa9

RIP: 0033:0x7f45a6fc41c9

RSP: 002b:00007ffc5a470218 EFLAGS: 00000246 ORIG_RAX: 0000000000000108

RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f45a6fc41c9

RDX: 0000000000000005 RSI: 0000000020000180 RDI: 0000000000000005

RBP: 00007ffc5a470240 R08: 00007ffc5a470160 R09: 0000000020000080

R10: 00000000200001c0 R11: 0000000000000246 R12: 0000000000400bb0

R13: 00007ffc5a470320 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:

page:00000000440015ce refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x10beee

flags: 0x200000000000000()

raw: 0200000000000000 ffffea00043ff4c8 ffffea0004325608 0000000000000000

raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88810beee580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

ffff88810beee600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

>ffff88810beee680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

^

ffff88810beee700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

ffff88810beee780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

==================================================================

Disabling lock debugging due to kernel taint

ext4_rename_dir_prepare: [2] parent_de->inode=3537895424

ext4_rename_dir_prepare: [3] dir=0xffff888124170140

ext4_rename_dir_prepare: [4] ino=2

ext4_rename_dir_prepare: ent->dir->i_ino=2 parent=-757071872

Reason is first directory entry which 'rec_len' is 34478, then will get illegal

parent entry. Now, we do not check directory entry after read directory block

in 'ext4_get_first_dir_block'.

To solve this issue, check directory entry in 'ext4_get_first_dir_block'.

[ Trigger an ext4_error() instead of just warning if the directory is

missing a '.' or '..' entry. Also make sure we return an error code

if the file system is corrupted. -TYT ]