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| author | Alexey Gladkov <legion@kernel.org> | 2021-07-08 12:33:01 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-07-08 11:43:24 -0700 |
| commit | f3791f4df569eadb3b1f5f2a247068d031fb91f5 (patch) | |
| tree | d126e8148da3fbf1d7a593246394b8772c3ca12f /lib/iommu-helper.c | |
| parent | e9f1cbc0c4114880090c7a578117d3b9cf184ad4 (diff) | |
| download | linux-f3791f4df569eadb3b1f5f2a247068d031fb91f5.tar.bz2 | |
Fix UCOUNT_RLIMIT_SIGPENDING counter leak
We must properly handle an errors when we increase the rlimit counter
and the ucounts reference counter. We have to this with RCU protection
to prevent possible use-after-free that could occur due to concurrent
put_cred_rcu().
The following reproducer triggers the problem:
$ cat testcase.sh
case "${STEP:-0}" in
0)
ulimit -Si 1
ulimit -Hi 1
STEP=1 unshare -rU "$0"
killall sleep
;;
1)
for i in 1 2 3 4 5; do unshare -rU sleep 5 & done
;;
esac
with the KASAN report being along the lines of
BUG: KASAN: use-after-free in put_ucounts+0x17/0xa0
Write of size 4 at addr ffff8880045f031c by task swapper/2/0
CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.13.0+ #19
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-alt4 04/01/2014
Call Trace:
<IRQ>
put_ucounts+0x17/0xa0
put_cred_rcu+0xd5/0x190
rcu_core+0x3bf/0xcb0
__do_softirq+0xe3/0x341
irq_exit_rcu+0xbe/0xe0
sysvec_apic_timer_interrupt+0x6a/0x90
</IRQ>
asm_sysvec_apic_timer_interrupt+0x12/0x20
default_idle_call+0x53/0x130
do_idle+0x311/0x3c0
cpu_startup_entry+0x14/0x20
secondary_startup_64_no_verify+0xc2/0xcb
Allocated by task 127:
kasan_save_stack+0x1b/0x40
__kasan_kmalloc+0x7c/0x90
alloc_ucounts+0x169/0x2b0
set_cred_ucounts+0xbb/0x170
ksys_unshare+0x24c/0x4e0
__x64_sys_unshare+0x16/0x20
do_syscall_64+0x37/0x70
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 0:
kasan_save_stack+0x1b/0x40
kasan_set_track+0x1c/0x30
kasan_set_free_info+0x20/0x30
__kasan_slab_free+0xeb/0x120
kfree+0xaa/0x460
put_cred_rcu+0xd5/0x190
rcu_core+0x3bf/0xcb0
__do_softirq+0xe3/0x341
The buggy address belongs to the object at ffff8880045f0300
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 28 bytes inside of
192-byte region [ffff8880045f0300, ffff8880045f03c0)
The buggy address belongs to the page:
page:000000008de0a388 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880045f0000 pfn:0x45f0
flags: 0x100000000000200(slab|node=0|zone=1)
raw: 0100000000000200 ffffea00000f4640 0000000a0000000a ffff888001042a00
raw: ffff8880045f0000 000000008010000d 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8880045f0200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880045f0280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8880045f0300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880045f0380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880045f0400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Disabling lock debugging due to kernel taint
Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts")
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/iommu-helper.c')
0 files changed, 0 insertions, 0 deletions