On Sat, Oct 2, 2021 at 2:41 AM Namjae Jeon <linkinjeon@xxxxxxxxxx> wrote:
>
> 2021-10-02 3:51 GMT+09:00, Marios Makassikis <mmakassikis@xxxxxxxxxx>:
> > On Mon, 2021-08-23 at 17:13 +0200, Christian Brauner wrote:
> >> From: Christian Brauner <christian.brauner@xxxxxxxxxx>
> >>
> >> Permission checking and copying over ownership information is the
> >> task
> >> of the underlying filesystem not ksmbd. The order is also wrong here.
> >> This modifies the inode before notify_change(). If notify_change()
> >> fails
> >> this will have changed ownership nonetheless. All of this is
> >> unnecessary
> >> though since the underlying filesystem's ->setattr handler will do
> >> all
> >> this (if required) by itself.
> >> Cc: Steve French <stfrench@xxxxxxxxxxxxx>
> >> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> >> Cc: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> >> Cc: Hyunchul Lee <hyc.lee@xxxxxxxxx>
> >> Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
> >> Cc: linux-cifs@xxxxxxxxxxxxxxx
> >> Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
> >> ---
> >> fs/ksmbd/smb2pdu.c | 5 -----
> >> 1 file changed, 5 deletions(-)
> >>
> >> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
> >> index 1148e52a4037..059764753aaa 100644
> >> --- a/fs/ksmbd/smb2pdu.c
> >> +++ b/fs/ksmbd/smb2pdu.c
> >> @@ -5521,12 +5521,7 @@ static int set_file_basic_info(struct
> >> ksmbd_file *fp, char *buf,
> >> if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
> >> return -EACCES;
> >>
> >> - rc = setattr_prepare(user_ns, dentry, &attrs);
> >> - if (rc)
> >> - return -EINVAL;
> >> -
> >> inode_lock(inode);
> >> - setattr_copy(user_ns, inode, &attrs);
> >> attrs.ia_valid &= ~ATTR_CTIME;
> >> rc = notify_change(user_ns, dentry, &attrs, NULL);
> >> inode_unlock(inode);
> >
> > Hello,
> Hi Marios,
> >
> > With this change, rsync'ing a large directory (kernel repo checkout for
> > example) to a FUSE-backed share crashes the kernel:
> >
> > BUG: unable to handle page fault for address: fffffffffffffff8
> > #PF: supervisor write access in kernel mode
> > #PF: error_code(0x0002) - not-present page
> > PGD 3229067 P4D 3229067 PUD 322b067 PMD 0
> > Oops: 0002 [#1] SMP KASAN NOPTI
> > CPU: 0 PID: 55 Comm: kworker/u2:1 Not tainted 5.15.0-rc3+ #186
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-
> > 1ubuntu1.1 04/01/2014
> > Workqueue: writeback wb_workfn (flush-8:17-fuseblk)
> > RIP: 0010:fuse_file_get+0x26/0x50
> > Code: 00 0f 1f 00 0f 1f 44 00 00 41 56 53 48 89 fb 4c 8d 77 28 4c 89
> > f7 be 04 00 00 00 e8 54 ad c1 ff be 01 00 00 00 b8 01 00 e
> > RSP: 0018:ffffc900001af660 EFLAGS: 00010256
> > RAX: 0000000000000001 RBX: ffffffffffffffd0 RCX: ffffffff818314cc
> > RDX: 0000000000000001 RSI: 0000000000000001 RDI: fffffffffffffff8
> > RBP: ffff8880108b0680 R08: dffffc0000000000 R09: fffffc0000000000
> > R10: fffffc0000000000 R11: 0000000000000000 R12: 0000000000000000
> > R13: 0000000000020087 R14: fffffffffffffff8 R15: ffff8880108b0680
> > FS: 0000000000000000(0000) GS:ffff888036200000(0000)
> > knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: fffffffffffffff8 CR3: 00000000101a4000 CR4: 00000000000006f0
> > Call Trace:
> > __fuse_write_file_get+0x4e/0x70
> > fuse_write_inode+0xf/0x40
> > __writeback_single_inode+0x206/0x250
> > writeback_sb_inodes+0x3fb/0x760
> > ? queue_io+0xd0/0xd0
> > ? trylock_super+0x17/0x60
> > ? __init_rwsem+0xf0/0xf0
> > ? rcu_read_lock_sched_held+0xa5/0x130
> > ? __bpf_trace_rcu_barrier+0x10/0x10
> > ? do_raw_spin_lock+0x14f/0x250
> > ? __bpf_trace_rcu_barrier+0x10/0x10
> > __writeback_inodes_wb+0xbf/0x130
> > wb_writeback+0x25b/0x360
> > ? print_irqtrace_events+0x110/0x110
> > ? trace_writeback_exec+0x150/0x150
> > ? _local_bh_enable+0x70/0x70
> > ? cpumask_next+0x20/0x50
> > ? cpumask_next+0x20/0x50
> > wb_workfn+0x608/0x860
> > ? __inode_wait_for_writeback+0x1c0/0x1c0
> > ? check_chain_key+0x1cf/0x2a0
> > ? __lock_acquire+0x9f4/0xdf0
> > ? lock_acquire+0x14d/0x370
> > ? process_one_work+0x2c5/0x550
> > ? lock_acquire+0x176/0x370
> > ? rcu_read_lock_sched_held+0xa5/0x130
> > ? __bpf_trace_rcu_barrier+0x10/0x10
> > ? lock_acquire+0x14d/0x370
> > ? worker_thread+0xf8/0x4a0
> > ? lock_acquire+0x176/0x370
> > process_one_work+0x304/0x550
> > ? worker_detach_from_pool+0x100/0x100
> > ? _raw_spin_lock_irq+0xaf/0xe0
> > ? _raw_spin_lock_irqsave+0xf0/0xf0
> > ? __list_add_valid+0x2a/0xa0
> > worker_thread+0x373/0x4a0
> > kthread+0x1d9/0x1f0
> > ? pr_cont_work+0xa0/0xa0
> > ? __list_add+0x50/0x50
> > ret_from_fork+0x1f/0x30
> > Modules linked in:
> > CR2: fffffffffffffff8
> > ---[ end trace fa4a96caf17482dd ]---
> >
> > $ ./scripts/faddr2line vmlinux.o fuse_file_get+0x26/0x50
> > fuse_file_get+0x26/0x50:
> > arch_atomic_fetch_add at arch/x86/include/asm/atomic.h:184
> > (inlined by) atomic_fetch_add_relaxed at include/asm-generic/atomic-
> > instrumented.h:143
> > (inlined by) __refcount_add at include/linux/refcount.h:193
> > (inlined by) __refcount_inc at include/linux/refcount.h:250
> > (inlined by) refcount_inc at include/linux/refcount.h:267
> > (inlined by) fuse_file_get at fs/fuse/file.c:93
> >
> > $ ./scripts/faddr2line vmlinux.o __fuse_write_file_get+0x4e/0x70
> > __fuse_write_file_get+0x4e/0x70:
> > __fuse_write_file_get at fs/fuse/file.c:1827
> >
> > I had already encountered this before [0]. Back then, changing ksmbd to
> > use notify_change rather than mark_inode_dirty fixed the issue [1].
> >
> > Using ext4/xfs does not trigger the bug.
> Thanks for your report and detailed check.
> >
> > rsync'ing the same folder over SMB (with samba4), or over NFS does not
> > trigger the bug either. The only combination where I'm seeing this so
> > far is ksmbd+FUSE, although I can't tell if it's a bug in ksmbd side or
> > FUSE.
>
> Could you please check your issue is fixed with the following change ?
Thanks for the quick reply. I did a few tests today and I can't reproduce
the crash after applying the patch. Is mark_inode_dirty() not needed here ?
>
> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
> index 4d1be224dd8e..e58a5a99d6ed 100644
> --- a/fs/ksmbd/smb2pdu.c
> +++ b/fs/ksmbd/smb2pdu.c
> @@ -5483,7 +5483,6 @@ static int set_file_basic_info(struct ksmbd_file *fp,
> struct ksmbd_share_config *share)
> {
> struct iattr attrs;
> - struct timespec64 ctime;
> struct file *filp;
> struct inode *inode;
> struct user_namespace *user_ns;
> @@ -5505,13 +5504,11 @@ static int set_file_basic_info(struct ksmbd_file *fp,
> attrs.ia_valid |= (ATTR_ATIME | ATTR_ATIME_SET);
> }
>
> + attrs.ia_valid |= ATTR_CTIME;
> if (file_info->ChangeTime) {
> attrs.ia_ctime = ksmbd_NTtimeToUnix(file_info->ChangeTime);
> - ctime = attrs.ia_ctime;
> - attrs.ia_valid |= ATTR_CTIME;
> - } else {
> - ctime = inode->i_ctime;
> - }
> + } else
> + attrs.ia_ctime = inode->i_ctime;
>
> if (file_info->LastWriteTime) {
> attrs.ia_mtime = ksmbd_NTtimeToUnix(file_info->LastWriteTime);
> @@ -5557,11 +5554,9 @@ static int set_file_basic_info(struct ksmbd_file *fp,
> return -EACCES;
>
> inode_lock(inode);
> + inode->i_ctime = attrs.ia_ctime;
> + attrs.ia_valid &= ~ATTR_CTIME;
> rc = notify_change(user_ns, dentry, &attrs, NULL);
> - if (!rc) {
> - inode->i_ctime = ctime;
> - mark_inode_dirty(inode);
> - }
> inode_unlock(inode);
> }
> return rc;
> --
> 2.25.1
>
> >
> > Marios
> >
> > [0]
> > https://lore.kernel.org/linux-fsdevel/CAF6XXKWCwqSa72p+iQjg4QSBmAkX4Y5DxGrRR1tW1ar2uthd=w@xxxxxxxxxxxxxx/T/#u
> > [1]
> > https://github.com/cifsd-team/ksmbd/commit/5e929125e519acaf48abc4c42f8389caa26c4d5a#diff-9f95c7d87d27c50e4e1d0afb24772b60bfa1449d619c118f23d7a2493d3ea9b0
> >
> >
