[PATCH 5.10.y] nilfs2: ignore non-fatal signals during synchronous log write wait

[Sasha Levin <sashal@kernel.org>]

From: Ryusuke Konishi <konishi.ryusuke@gmail.com>

[ Upstream commit 7131aaa74bcc7c9da1f1d1c8724da75c775557a0 ]

Based on a syzbot report, Wang Jianjian pointed out that following a
successful directory operation in nilfs_rename(), a synchronous write
requested within nilfs_transaction_commit(), triggered by a sync flag
set by nilfs_commit_chunk(), could be interrupted by a user signal.
This interruption leaves in-memory metadata updates intact while
returning an error, causing inconsistency with the VFS dentry cache and
ultimately triggering a kernel warning.

According to "signal(7)", local disks are not classified as "slow
devices" (such as terminals, FIFOs, or pipes) and their I/O operations
on disk devices are not interrupted by signals.  In kernel space,
waiting for such disk I/O should therefore not be aborted by ordinary
(non-fatal) signals.

Suppress this issue by modifying nilfs_segctor_sync(), which waits for
the log writer thread to complete synchronous writes, to catch only
fatal signals via fatal_signal_pending() and return -EINTR rather than
-ERESTARTSYS.  To complement this change and prevent the wait loop from
busy-looping when schedule() returns immediately due to a pending
non-fatal signal, switch the wait state from TASK_INTERRUPTIBLE to
TASK_KILLABLE.

This serves as an effective interim stabilization measure without
structural changes until a comprehensive fix for metadata consistency
is implemented.

Reported-by: syzbot+f6c7e1f1809f235eeb90@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f6c7e1f1809f235eeb90
Fixes: 9ff05123e3bf ("nilfs2: segment constructor")
Tested-by: syzbot+f6c7e1f1809f235eeb90@syzkaller.appspotmail.com
Cc: Wang Jianjian <wangjianjian3@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
[ sashal: preserved the older return-code comment layout instead of upstream's reformatted lists ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nilfs2/ioctl.c    |  2 +-
 fs/nilfs2/recovery.c |  2 +-
 fs/nilfs2/segment.c  | 10 +++++-----
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 9f10a9cec3e0a..e6db5b8190e3c 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -1011,7 +1011,7 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
  *
  * %-ENOSPC - No space left on device (only in a panic state).
  *
- * %-ERESTARTSYS - Interrupted.
+ * %-EINTR - Interrupted.
  *
  * %-ENOMEM - Insufficient memory available.
  *
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
index 33c4a97519de8..bf64a9eff4d15 100644
--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -750,7 +750,7 @@ static void nilfs_abort_roll_forward(struct the_nilfs *nilfs)
  *
  * %-ENOSPC - No space left on device (only in a panic state).
  *
- * %-ERESTARTSYS - Interrupted.
+ * %-EINTR - Interrupted.
  *
  * %-ENOMEM - Insufficient memory available.
  */
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 18964331ee3d9..cc12f4dd2eee2 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2236,7 +2236,7 @@ static int nilfs_segctor_sync(struct nilfs_sc_info *sci)
 	wake_up(&sci->sc_wait_daemon);
 
 	for (;;) {
-		set_current_state(TASK_INTERRUPTIBLE);
+		set_current_state(TASK_KILLABLE);
 
 		/*
 		 * Synchronize only while the log writer thread is alive.
@@ -2250,11 +2250,11 @@ static int nilfs_segctor_sync(struct nilfs_sc_info *sci)
 			err = wait_req.err;
 			break;
 		}
-		if (!signal_pending(current)) {
+		if (!fatal_signal_pending(current)) {
 			schedule();
 			continue;
 		}
-		err = -ERESTARTSYS;
+		err = -EINTR;
 		break;
 	}
 	finish_wait(&sci->sc_wait_request, &wait_req.wq);
@@ -2295,7 +2295,7 @@ static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err, bool force)
  *
  * %-ENOSPC - No space left on device (only in a panic state).
  *
- * %-ERESTARTSYS - Interrupted.
+ * %-EINTR - Interrupted.
  *
  * %-ENOMEM - Insufficient memory available.
  */
@@ -2332,7 +2332,7 @@ int nilfs_construct_segment(struct super_block *sb)
  *
  * %-ENOSPC - No space left on device (only in a panic state).
  *
- * %-ERESTARTSYS - Interrupted.
+ * %-EINTR - Interrupted.
  *
  * %-ENOMEM - Insufficient memory available.
  */
-- 
2.53.0