CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
AI Score
Confidence
Low
EPSS
Percentile
5.0%
In the Linux kernel, the following vulnerability has been resolved:
cachefiles: fix slab-use-after-free in cachefiles_withdraw_cookie()
We got the following issue in our fault injection stress test:
==================================================================
BUG: KASAN: slab-use-after-free in cachefiles_withdraw_cookie+0x4d9/0x600
Read of size 8 at addr ffff888118efc000 by task kworker/u78:0/109
CPU: 13 PID: 109 Comm: kworker/u78:0 Not tainted 6.8.0-dirty #566
Call Trace:
<TASK>
kasan_report+0x93/0xc0
cachefiles_withdraw_cookie+0x4d9/0x600
fscache_cookie_state_machine+0x5c8/0x1230
fscache_cookie_worker+0x91/0x1c0
process_one_work+0x7fa/0x1800
[…]
Allocated by task 117:
kmalloc_trace+0x1b3/0x3c0
cachefiles_acquire_volume+0xf3/0x9c0
fscache_create_volume_work+0x97/0x150
process_one_work+0x7fa/0x1800
[…]
Following is the process that triggers the issue:
p1 | p2
fscache_begin_lookup
fscache_begin_volume_access
fscache_cache_is_live(fscache_cache)
cachefiles_daemon_release
cachefiles_put_unbind_pincount
cachefiles_daemon_unbind
cachefiles_withdraw_cache
fscache_withdraw_cache
fscache_set_cache_state(cache, FSCACHE_CACHE_IS_WITHDRAWN);
cachefiles_withdraw_objects(cache)
fscache_wait_for_objects(fscache)
atomic_read(&fscache_cache->object_count) == 0
fscache_perform_lookup
cachefiles_lookup_cookie
cachefiles_alloc_object
refcount_set(&object->ref, 1);
object->volume = volume
fscache_count_object(vcookie->cache);
atomic_inc(&fscache_cache->object_count)
cachefiles_withdraw_volumes
cachefiles_withdraw_volume
fscache_withdraw_volume
__cachefiles_free_volume
kfree(cachefiles_volume)
fscache_cookie_state_machine
cachefiles_withdraw_cookie
cache = object->volume->cache;
// cachefiles_volume UAF !!!
After setting FSCACHE_CACHE_IS_WITHDRAWN, wait for all the cookie lookups
to complete first, and then wait for fscache_cache->object_count == 0 to
avoid the cookie exiting after the volume has been freed and triggering
the above issue. Therefore call fscache_withdraw_volume() before calling
cachefiles_withdraw_objects().
This way, after setting FSCACHE_CACHE_IS_WITHDRAWN, only the following two
cases will occur:
Vendor | Product | Version | CPE |
---|---|---|---|
linux | linux_kernel | * | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
[
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"fs/cachefiles/cache.c",
"fs/cachefiles/volume.c"
],
"versions": [
{
"version": "fe2140e2f57f",
"lessThan": "8de253177112",
"status": "affected",
"versionType": "git"
},
{
"version": "fe2140e2f57f",
"lessThan": "9e67589a4a7b",
"status": "affected",
"versionType": "git"
},
{
"version": "fe2140e2f57f",
"lessThan": "ef81340401e8",
"status": "affected",
"versionType": "git"
},
{
"version": "fe2140e2f57f",
"lessThan": "5d8f80578907",
"status": "affected",
"versionType": "git"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"fs/cachefiles/cache.c",
"fs/cachefiles/volume.c"
],
"versions": [
{
"version": "5.17",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.17",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.1.101",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.6.42",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.9.11",
"lessThanOrEqual": "6.9.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.10",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
]