Messages in this thread | | | From | (Eric W. Biederman) | Date | Sun, 19 Dec 2021 23:58:41 -0600 | Subject | Re: BUG: KASAN: use-after-free in dec_rlimit_ucounts |
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Qian Cai <quic_qiancai@quicinc.com> writes:
> On Wed, Nov 24, 2021 at 04:49:19PM -0500, Qian Cai wrote: >> Hmm, I don't know if that or it is just this platfrom is lucky to trigger >> the race condition quickly, but I can't reproduce it on x86 so far. I am >> Cc'ing a few arm64 people to see if they have spot anything I might be >> missing. The original bug report is here: >> >> https://lore.kernel.org/lkml/YZV7Z+yXbsx9p3JN@fixkernel.com/ > > Okay, I am finally able to reproduce this on x86_64 with the latest > mainline as well by setting CONFIG_USER_NS and KASAN on the top of > defconfig (I did not realize it did not select CONFIG_USER_NS in the first > place). Anyway, it still took less than 5-minute by running: > > $ trinity -C 48
It took me a while to get to the point of reproducing this but I can confirm I see this with 2 core VM, running 5.16.0-rc4.
Running trinity 2019.06 packaged in debian 11.
I didn't watch so I don't know if it was 5 minutes but I do know it took less than an hour.
Now I am puzzled why there are not other reports of problems.
Now to start drilling down to figure out why the user namespace was freed early. ----
The failure I got looked like: > BUG: KASAN: use-after-free in dec_rlimit_ucounts+0x7b/0xb0 > Read of size 8 at addr ffff88800b7dd018 by task trinity-c3/67982 > > CPU: 1 PID: 67982 Comm: trinity-c3 Tainted: G O 5.16.0-rc4 #1 > Hardware name: Xen HVM domU, BIOS 4.8.5-35.fc25 08/25/2021 > Call Trace: > <TASK> > dump_stack_lvl+0x48/0x5e > print_address_descrtion.constprop.0+0x1f/0x140 > ? dec_rlimit_ucounts+0x7b/0xb0 > ? dec_rlimit_ucounts+0x7b/0xb0 > kasan_report.cold+0x7f/0xe0 > ? _raw_spin_lock+0x7f/0x11b > ? dec_rlimit_ucounts+0x7b/0xb0 > dec_rlimit_ucounts+0x7b/0xb0 > mqueue_evict_inode+0x417/0x590 > ? perf_trace_global_dirty_state+0x350/0x350 > ? __x64_sys_mq_unlink+0x250/0x250 > ? _raw_spin_lock_bh+0xe0/0xe0 > ? _raw_spin_lock_bh+0xe0/0xe0 > evict+0x155/0x2a0 > __x64_sys_mq_unlink+0x1a7/0x250 > do_syscall_64+0x3b/0x90 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7f0505ebc9b9 > Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 00 0f 1f 44 00 00 48 89 .... > > Allocated by task 67717 > Freed by task 6027 > > The buggy address belongs to the object at ffff88800b7dce38 > which belongs to the cache user_namespace of size 600 > The buggy address is located 480 bytes inside of > 600-byte region [ffff88800b7dce38, ffff88800b7dd090] > The buggy address belongs to the page: > > trinity: Detected kernel tainting. Last seed was 1891442794
Eric
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