Headline
CVE-2023-45898: ext4: fix slab-use-after-free in ext4_es_insert_extent() · torvalds/linux@768d612
The Linux kernel before 6.5.4 has an es1 use-after-free in fs/ext4/extents_status.c, related to ext4_es_insert_extent.
Commit
Permalink
Browse files
Browse the repository at this point in the history
ext4: fix slab-use-after-free in ext4_es_insert_extent()
Yikebaer reported an issue:
BUG: KASAN: slab-use-after-free in ext4_es_insert_extent+0xc68/0xcb0 fs/ext4/extents_status.c:894 Read of size 4 at addr ffff888112ecc1a4 by task syz-executor/8438
CPU: 1 PID: 8438 Comm: syz-executor Not tainted 6.5.0-rc5 #1 Call Trace: […] kasan_report+0xba/0xf0 mm/kasan/report.c:588 ext4_es_insert_extent+0xc68/0xcb0 fs/ext4/extents_status.c:894 ext4_map_blocks+0x92a/0x16f0 fs/ext4/inode.c:680 ext4_alloc_file_blocks.isra.0+0x2df/0xb70 fs/ext4/extents.c:4462 ext4_zero_range fs/ext4/extents.c:4622 [inline] ext4_fallocate+0x251c/0x3ce0 fs/ext4/extents.c:4721 […]
Allocated by task 8438: […] kmem_cache_zalloc include/linux/slab.h:693 [inline] __es_alloc_extent fs/ext4/extents_status.c:469 [inline] ext4_es_insert_extent+0x672/0xcb0 fs/ext4/extents_status.c:873 ext4_map_blocks+0x92a/0x16f0 fs/ext4/inode.c:680 ext4_alloc_file_blocks.isra.0+0x2df/0xb70 fs/ext4/extents.c:4462 ext4_zero_range fs/ext4/extents.c:4622 [inline] ext4_fallocate+0x251c/0x3ce0 fs/ext4/extents.c:4721 […]
Freed by task 8438: […] kmem_cache_free+0xec/0x490 mm/slub.c:3823 ext4_es_try_to_merge_right fs/ext4/extents_status.c:593 [inline] __es_insert_extent+0x9f4/0x1440 fs/ext4/extents_status.c:802 ext4_es_insert_extent+0x2ca/0xcb0 fs/ext4/extents_status.c:882 ext4_map_blocks+0x92a/0x16f0 fs/ext4/inode.c:680 ext4_alloc_file_blocks.isra.0+0x2df/0xb70 fs/ext4/extents.c:4462 ext4_zero_range fs/ext4/extents.c:4622 [inline] ext4_fallocate+0x251c/0x3ce0 fs/ext4/extents.c:4721 […] ==================================================================
The flow of issue triggering is as follows:
remove es raw es es removed es1 |-------------------| -> |----|…|------|
insert es es insert es1 merge with es es1 merge with es and free es1 |----|…|------| -> |------------|------| -> |-------------------|
es merges with newes, then merges with es1, frees es1, then determines if es1->es_len is 0 and triggers a UAF.
The code flow is as follows: ext4_es_insert_extent es1 = __es_alloc_extent(true); es2 = __es_alloc_extent(true); __es_remove_extent(inode, lblk, end, NULL, es1) __es_insert_extent(inode, &newes, es1) —> insert es1 to es tree __es_insert_extent(inode, &newes, es2) ext4_es_try_to_merge_right ext4_es_free_extent(inode, es1) —> es1 is freed if (es1 && !es1->es_len) // Trigger UAF by determining if es1 is used.
We determine whether es1 or es2 is used immediately after calling __es_remove_extent() or __es_insert_extent() to avoid triggering a UAF if es1 or es2 is freed.
Reported-by: Yikebaer Aizezi [email protected] Closes: https://lore.kernel.org/lkml/CALcu4raD4h9coiyEBL4Bm0zjDwxC2CyPiTwsP3zFuhot6y9Beg@mail.gmail.com Fixes: 2a69c45 ("ext4: using nofail preallocation in ext4_es_insert_extent()") Cc: [email protected] Signed-off-by: Baokun Li [email protected] Reviewed-by: Jan Kara [email protected] Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Theodore Ts’o [email protected]
- Loading branch information
Related news
Ubuntu Security Notice 6573-1 - Lucas Leong discovered that the netfilter subsystem in the Linux kernel did not properly validate some attributes passed from userspace. A local attacker could use this to cause a denial of service or possibly expose sensitive information. Kyle Zeng discovered that the IPv4 implementation in the Linux kernel did not properly handle socket buffers when performing IP routing in certain circumstances, leading to a null pointer dereference vulnerability. A privileged attacker could use this to cause a denial of service.
Ubuntu Security Notice 6537-1 - Yu Hao discovered that the UBI driver in the Linux kernel did not properly check for MTD with zero erasesize during device attachment. A local privileged attacker could use this to cause a denial of service. Lucas Leong discovered that the netfilter subsystem in the Linux kernel did not properly validate some attributes passed from userspace. A local attacker could use this to cause a denial of service or possibly expose sensitive information.
Ubuntu Security Notice 6536-1 - Lucas Leong discovered that the netfilter subsystem in the Linux kernel did not properly validate some attributes passed from userspace. A local attacker could use this to cause a denial of service or possibly expose sensitive information. Kyle Zeng discovered that the IPv4 implementation in the Linux kernel did not properly handle socket buffers when performing IP routing in certain circumstances, leading to a null pointer dereference vulnerability. A privileged attacker could use this to cause a denial of service.