Messages in this thread | | | Date | Mon, 15 Nov 2021 08:38:38 -0800 | Subject | Re: [PATCH] io_uring: prevent io_put_identity() from freeing a static identity | From | Tadeusz Struk <> |
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On 11/3/21 18:21, Tadeusz Struk wrote: > Note: this applies to 5.10 stable only. It doesn't trigger on anything > above 5.10 as the code there has been substantially reworked. This also > doesn't apply to any stable kernel below 5.10 afaict. > > Syzbot found a bug: KASAN: invalid-free in io_dismantle_req > https://syzkaller.appspot.com/bug?id=123d9a852fc88ba573ffcb2dbcf4f9576c3b0559 > > The test submits bunch of io_uring writes and exits, which then triggers > uring_task_cancel() and io_put_identity(), which in some corner cases, > tries to free a static identity. This causes a panic as shown in the > trace below: > > BUG: KASAN: double-free or invalid-free in kfree+0xd5/0x310 > CPU: 0 PID: 4618 Comm: repro Not tainted 5.10.76-05281-g4944ec82ebb9-dirty #17 > Call Trace: > dump_stack_lvl+0x1b2/0x21b > print_address_description+0x8d/0x3b0 > kasan_report_invalid_free+0x58/0x130 > ____kasan_slab_free+0x14b/0x170 > __kasan_slab_free+0x11/0x20 > slab_free_freelist_hook+0xcc/0x1a0 > kfree+0xd5/0x310 > io_dismantle_req+0x9b0/0xd90 > io_do_iopoll+0x13a4/0x23e0 > io_iopoll_try_reap_events+0x116/0x290 > io_uring_cancel_task_requests+0x197d/0x1ee0 > io_uring_flush+0x170/0x6d0 > filp_close+0xb0/0x150 > put_files_struct+0x1d4/0x350 > exit_files+0x80/0xa0 > do_exit+0x6d9/0x2390 > do_group_exit+0x16a/0x2d0 > get_signal+0x133e/0x1f80 > arch_do_signal+0x7b/0x610 > exit_to_user_mode_prepare+0xaa/0xe0 > syscall_exit_to_user_mode+0x24/0x40 > do_syscall_64+0x3d/0x70 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Allocated by task 4611: > ____kasan_kmalloc+0xcd/0x100 > __kasan_kmalloc+0x9/0x10 > kmem_cache_alloc_trace+0x208/0x390 > io_uring_alloc_task_context+0x57/0x550 > io_uring_add_task_file+0x1f7/0x290 > io_uring_create+0x2195/0x3490 > __x64_sys_io_uring_setup+0x1bf/0x280 > do_syscall_64+0x31/0x70 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > The buggy address belongs to the object at ffff88810732b500 > which belongs to the cache kmalloc-192 of size 192 > The buggy address is located 88 bytes inside of > 192-byte region [ffff88810732b500, ffff88810732b5c0) > Kernel panic - not syncing: panic_on_warn set ... > > This issue bisected to this commit: > commit 186725a80c4e ("io_uring: fix skipping disabling sqo on exec") > > Simple reverting the offending commit doesn't work as it hits some > other, related issues like: > > /* sqo_dead check is for when this happens after cancellation */ > WARN_ON_ONCE(ctx->sqo_task == current && !ctx->sqo_dead && > !xa_load(&tctx->xa, (unsigned long)file)); > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 5622 at fs/io_uring.c:8960 io_uring_flush+0x5bc/0x6d0 > Modules linked in: > CPU: 1 PID: 5622 Comm: repro Not tainted 5.10.76-05281-g4944ec82ebb9-dirty #16 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-6.fc35 04/01/2014 > RIP: 0010:io_uring_flush+0x5bc/0x6d0 > Call Trace: > filp_close+0xb0/0x150 > put_files_struct+0x1d4/0x350 > reset_files_struct+0x88/0xa0 > bprm_execve+0x7f2/0x9f0 > do_execveat_common+0x46f/0x5d0 > __x64_sys_execve+0x92/0xb0 > do_syscall_64+0x31/0x70 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Changing __io_uring_task_cancel() to call io_disable_sqo_submit() directly, > as the comment suggests, only if __io_uring_files_cancel() is not executed > seems to fix the issue. > > Cc: Jens Axboe <axboe@kernel.dk> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: <io-uring@vger.kernel.org> > Cc: <linux-fsdevel@vger.kernel.org> > Cc: <linux-kernel@vger.kernel.org> > Cc: <stable@vger.kernel.org> > Reported-by: syzbot+6055980d041c8ac23307@syzkaller.appspotmail.com > Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org> > --- > fs/io_uring.c | 21 +++++++++++++++++---- > 1 file changed, 17 insertions(+), 4 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 0736487165da..fcf9ffe9b209 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -8882,20 +8882,18 @@ void __io_uring_task_cancel(void) > struct io_uring_task *tctx = current->io_uring; > DEFINE_WAIT(wait); > s64 inflight; > + int canceled = 0; > > /* make sure overflow events are dropped */ > atomic_inc(&tctx->in_idle); > > - /* trigger io_disable_sqo_submit() */ > - if (tctx->sqpoll) > - __io_uring_files_cancel(NULL); > - > do { > /* read completions before cancelations */ > inflight = tctx_inflight(tctx); > if (!inflight) > break; > __io_uring_files_cancel(NULL); > + canceled = 1; > > prepare_to_wait(&tctx->wait, &wait, TASK_UNINTERRUPTIBLE); > > @@ -8909,6 +8907,21 @@ void __io_uring_task_cancel(void) > finish_wait(&tctx->wait, &wait); > } while (1); > > + /* > + * trigger io_disable_sqo_submit() > + * if not already done by __io_uring_files_cancel() > + */ > + if (tctx->sqpoll && !canceled) { > + struct file *file; > + unsigned long index; > + > + xa_for_each(&tctx->xa, index, file) { > + struct io_ring_ctx *ctx = file->private_data; > + > + io_disable_sqo_submit(ctx); > + } > + } > + > atomic_dec(&tctx->in_idle); > > io_uring_remove_task_files(tctx); >
Hi, Any comments on this one? It needs to be ACK'ed by the maintainer before it is applied to 5.10 stable.
-- Thanks, Tadeusz
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