CVE-2022-49349

Summary

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 ]

Affected Software

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: total

References

• https://git.kernel.org/stable/c/1a3a15bf6f9963d755270cbdb282863b84839195
• https://git.kernel.org/stable/c/97f802a652a749422dede32071d29a53cf4bd034
• https://git.kernel.org/stable/c/10801095224de0d0ab06ae60698680c1f883a3ae
• https://git.kernel.org/stable/c/eaecf7ebfd5dd09038a80b14be46b844f54cfc5c
• https://git.kernel.org/stable/c/dd887f83ea54aea5b780a84527e23ab95f777fed
• https://git.kernel.org/stable/c/364380c00912bed9b5d99eb485018360b0ecf64f
• https://git.kernel.org/stable/c/0ff38b99fa075ddd246487a28cb9af049f4ceef1
• https://git.kernel.org/stable/c/4a2bea60cf7ff957b3eda0b17750d483876a02fa
• https://git.kernel.org/stable/c/0be698ecbe4471fcad80e81ec6a05001421041b3

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