On Wed, 2024-10-09 at 11:02 +0800, yangerkun wrote:
> Hi,
>
> Ping for this patch...
>
> 在 2024/9/29 9:45, yangerkun 写道:
> >
> >
> > 在 2024/9/29 9:38, yangerkun 写道:
> > >
> > >
> > > 在 2024/9/28 4:58, Anna Schumaker 写道:
> > > > Hi Yang,
> > > >
> > > > On 9/26/24 2:12 AM, Yang Erkun wrote:
> > > > > From: Yang Erkun <yangerkun@xxxxxxxxxx>
> > > > >
> > > > > Two threads that work with the same cred try to open
> > > > > different files
> > > > > concurrently, they will utilize the same nfs4_state_owner.
> > > > > And in order
> > > > > to sequential open request send to server, the second task
> > > > > will fall
> > > > > into RPC_TASK_QUEUED in nfs_wait_on_sequence since there is
> > > > > already one
> > > > > work doing the open operation. Furthermore, the second task
> > > > > will wait
> > > > > until the first task completes its work, call
> > > > > rpc_wake_up_queued_task in
> > > > > nfs_release_seqid to wake up the second task, allowing it to
> > > > > complete
> > > > > the remaining open operation.
> > > > >
> > > > > The preceding logic does not cause any problems under normal
> > > > > circumstances. However, when once we force an unmount using
> > > > > `umount
> > > > > -f`,
> > > > > the function nfs_umount_begin attempts to kill all tasks by
> > > > > calling
> > > > > rpc_signal_task. This help wake up the second task, but it
> > > > > sets the
> > > > > status to -ERESTARTSYS. This status prevents
> > > > > `nfs4_open_release` from
> > > > > calling `nfs4_opendata_to_nfs4_state`. Consequently, while
> > > > > the second
> > > > > task will be freed, the original tasks will still exist in
> > > > > sequence->list(see nfs_release_seqid). Latter, when the first
> > > > > thread
> > > > > calls nfs_release_seqid and attempts to wake up the second
> > > > > task, it
> > > > > will
> > > > > trigger the uaf.
> > > > >
> > > > > To resolve this issue, ensure rpc_task will remove it from
> > > > > sequence->list by adding nfs_release_seqid in
> > > > > nfs4_open_release.
> > > > >
> > > > > =============================================================
> > > > > =====
> > > > > BUG: KASAN: slab-use-after-free in
> > > > > rpc_wake_up_queued_task+0xbb/0xc0
> > > > > Read of size 8 at addr ff11000007639930 by task bash/792
> > > > >
> > > > > CPU: 0 UID: 0 PID: 792 Comm: bash Tainted: G B W
> > > > > 6.11.0-09960-gd10b58fe53dc-dirty #10
> > > > > Tainted: [B]=BAD_PAGE, [W]=WARN
> > > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > > > 1.16.1-2.fc37 04/01/2014
> > > > > Call Trace:
> > > > > <TASK>
> > > > > dump_stack_lvl+0xa3/0x120
> > > > > print_address_description.constprop.0+0x63/0x510
> > > > > print_report+0xf5/0x360
> > > > > kasan_report+0xd9/0x140
> > > > > __asan_report_load8_noabort+0x24/0x40
> > > > > rpc_wake_up_queued_task+0xbb/0xc0
> > > > > nfs_release_seqid+0x1e1/0x2f0
> > > > > nfs_free_seqid+0x1a/0x40
> > > > > nfs4_opendata_free+0xc6/0x3e0
> > > > > _nfs4_do_open.isra.0+0xbe3/0x1380
> > > > > nfs4_do_open+0x28b/0x620
> > > > > nfs4_atomic_open+0x2c6/0x3a0
> > > > > nfs_atomic_open+0x4f8/0x1180
> > > > > atomic_open+0x186/0x4e0
> > > > > lookup_open.isra.0+0x3e7/0x15b0
> > > > > open_last_lookups+0x85d/0x1260
> > > > > path_openat+0x151/0x7b0
> > > > > do_filp_open+0x1e0/0x310
> > > > > do_sys_openat2+0x178/0x1f0
> > > > > do_sys_open+0xa2/0x100
> > > > > __x64_sys_openat+0xa8/0x120
> > > > > x64_sys_call+0x2507/0x4540
> > > > > do_syscall_64+0xa7/0x240
> > > > > entry_SYSCALL_64_after_hwframe+0x76/0x7e
> > > > >
> > > > > ...
> > > > >
> > > > > Allocated by task 767:
> > > > > kasan_save_stack+0x3b/0x70
> > > > > kasan_save_track+0x1c/0x40
> > > > > kasan_save_alloc_info+0x44/0x70
> > > > > __kasan_slab_alloc+0xaf/0xc0
> > > > > kmem_cache_alloc_noprof+0x1e0/0x4f0
> > > > > rpc_new_task+0xe7/0x220
> > > > > rpc_run_task+0x27/0x7d0
> > > > > nfs4_run_open_task+0x477/0x810
> > > > > _nfs4_proc_open+0xc0/0x6d0
> > > > > _nfs4_open_and_get_state+0x178/0xc50
> > > > > _nfs4_do_open.isra.0+0x47f/0x1380
> > > > > nfs4_do_open+0x28b/0x620
> > > > > nfs4_atomic_open+0x2c6/0x3a0
> > > > > nfs_atomic_open+0x4f8/0x1180
> > > > > atomic_open+0x186/0x4e0
> > > > > lookup_open.isra.0+0x3e7/0x15b0
> > > > > open_last_lookups+0x85d/0x1260
> > > > > path_openat+0x151/0x7b0
> > > > > do_filp_open+0x1e0/0x310
> > > > > do_sys_openat2+0x178/0x1f0
> > > > > do_sys_open+0xa2/0x100
> > > > > __x64_sys_openat+0xa8/0x120
> > > > > x64_sys_call+0x2507/0x4540
> > > > > do_syscall_64+0xa7/0x240
> > > > > entry_SYSCALL_64_after_hwframe+0x76/0x7e
> > > > >
> > > > > Freed by task 767:
> > > > > kasan_save_stack+0x3b/0x70
> > > > > kasan_save_track+0x1c/0x40
> > > > > kasan_save_free_info+0x43/0x80
> > > > > __kasan_slab_free+0x4f/0x90
> > > > > kmem_cache_free+0x199/0x4f0
> > > > > mempool_free_slab+0x1f/0x30
> > > > > mempool_free+0xdf/0x3d0
> > > > > rpc_free_task+0x12d/0x180
> > > > > rpc_final_put_task+0x10e/0x150
> > > > > rpc_do_put_task+0x63/0x80
> > > > > rpc_put_task+0x18/0x30
> > > > > nfs4_run_open_task+0x4f4/0x810
> > > > > _nfs4_proc_open+0xc0/0x6d0
> > > > > _nfs4_open_and_get_state+0x178/0xc50
> > > > > _nfs4_do_open.isra.0+0x47f/0x1380
> > > > > nfs4_do_open+0x28b/0x620
> > > > > nfs4_atomic_open+0x2c6/0x3a0
> > > > > nfs_atomic_open+0x4f8/0x1180
> > > > > atomic_open+0x186/0x4e0
> > > > > lookup_open.isra.0+0x3e7/0x15b0
> > > > > open_last_lookups+0x85d/0x1260
> > > > > path_openat+0x151/0x7b0
> > > > > do_filp_open+0x1e0/0x310
> > > > > do_sys_openat2+0x178/0x1f0
> > > > > do_sys_open+0xa2/0x100
> > > > > __x64_sys_openat+0xa8/0x120
> > > > > x64_sys_call+0x2507/0x4540
> > > > > do_syscall_64+0xa7/0x240
> > > > > entry_SYSCALL_64_after_hwframe+0x76/0x7e
> > > >
> > > > Once I apply this patch I'm seeing my client hang when running
> > > > xfstests generic/451 with NFS v4.0. I was wondering if you
> > > > could
> > > > check if you see the same hang, and please fix it if so?
> > > >
> > >
> > > I have try to reproduce this with kernel commit:
> >
> > Forget to say, add this patch too...
> >
> > >
> > > commit abf2050f51fdca0fd146388f83cddd95a57a008d
> > > Merge: 9ab27b018649 81ee62e8d09e
> > > Author: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > > Date: Mon Sep 23 15:27:58 2024 -0700
> > >
> > > Merge tag 'media/v6.12-1' of
> > > git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
> > >
> > > And for nfs4.0/nfs4.1, all seems ok now...
> > >
> > > Can you provide more info about the 'hang' you meet now?
> > >
> > >
> > > > Thanks,
> > > > Anna
> > > >
> > > > >
> > > > > Fixes: 24ac23ab88df ("NFSv4: Convert open() into an
> > > > > asynchronous RPC
> > > > > call")
> > > > > Signed-off-by: Yang Erkun <yangerkun@xxxxxxxxxx>
> > > > > ---
> > > > > fs/nfs/nfs4proc.c | 1 +
> > > > > 1 file changed, 1 insertion(+)
> > > > >
> > > > > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> > > > > index b8ffbe52ba15..4685621ba469 100644
> > > > > --- a/fs/nfs/nfs4proc.c
> > > > > +++ b/fs/nfs/nfs4proc.c
> > > > > @@ -2603,6 +2603,7 @@ static void nfs4_open_release(void
> > > > > *calldata)
> > > > > struct nfs4_opendata *data = calldata;
> > > > > struct nfs4_state *state = NULL;
> > > > > + nfs_release_seqid(data->o_arg.seqid);
> > > > > /* If this request hasn't been cancelled, do nothing */
> > > > > if (!data->cancelled)
> > > > > goto out_free;
>
If the OPEN was successful, but asked us to confirm the sequence id, we
can end up releasing the sequence before we've been able to call
open_confirm if we do the above. I suspect this is why Anna is seeing
the hang when running xfstests.
I think we rather want to check if (task->tk_status != 0 && !data-
>rpc_done) before calling nfs_release_seqid() above, since that might
correspond to the case where we interrupted the RPC call before it gets
to the front of the list, but will never correspond to the case where
we need to confirm the sequence.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
