[PATCH 5.15.y 2/2] 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>
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 baa43a13b7a87..3f3909b77bcdf 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -960,10 +960,10 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
  * Return: 0 on success, or one of the following negative error codes on
  * failure:
  * * %-EFAULT		- Failure during execution of requested operation.
+ * * %-EINTR		- Interrupted.
  * * %-EIO		- I/O error.
  * * %-ENOMEM		- Insufficient memory available.
  * * %-ENOSPC		- No space left on device (only in a panic state).
- * * %-ERESTARTSYS	- Interrupted.
  * * %-EROFS		- Read only filesystem.
  */
 static int nilfs_ioctl_sync(struct inode *inode, struct file *filp,
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
index 10c59d2c83447..0f5161df0709b 100644
--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -743,11 +743,11 @@ static void nilfs_abort_roll_forward(struct the_nilfs *nilfs)
  *
  * Return: 0 on success, or one of the following negative error codes on
  * failure:
+ * * %-EINTR		- Interrupted.
  * * %-EINVAL		- Inconsistent filesystem state.
  * * %-EIO		- I/O error.
  * * %-ENOMEM		- Insufficient memory available.
  * * %-ENOSPC		- No space left on device (only in a panic state).
- * * %-ERESTARTSYS	- Interrupted.
  */
 int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs,
 			      struct super_block *sb,
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index a1a091a20d041..3efadc2c6a031 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2234,7 +2234,7 @@ 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.
@@ -2248,11 +2248,11 @@ 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);
@@ -2286,10 +2286,10 @@ static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err, bool force)
  *
  * Return: 0 on success, or one of the following negative error codes on
  * failure:
+ * * %-EINTR		- Interrupted.
  * * %-EIO		- I/O error (including metadata corruption).
  * * %-ENOMEM		- Insufficient memory available.
  * * %-ENOSPC		- No space left on device (only in a panic state).
- * * %-ERESTARTSYS	- Interrupted.
  * * %-EROFS		- Read only filesystem.
  */
 int nilfs_construct_segment(struct super_block *sb)
@@ -2318,10 +2318,10 @@ int nilfs_construct_segment(struct super_block *sb)
  *
  * Return: 0 on success, or one of the following negative error codes on
  * failure:
+ * * %-EINTR		- Interrupted.
  * * %-EIO		- I/O error (including metadata corruption).
  * * %-ENOMEM		- Insufficient memory available.
  * * %-ENOSPC		- No space left on device (only in a panic state).
- * * %-ERESTARTSYS	- Interrupted.
  * * %-EROFS		- Read only filesystem.
  */
 int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
-- 
2.53.0