From: Qianchang Zhao <pioooooooooip@gmail.com>
To: Namjae Jeon <linkinjeon@kernel.org>, Steve French <smfrench@gmail.com>
Cc: gregkh@linuxfoundation.org, linux-cifs@vger.kernel.org,
linux-kernel@vger.kernel.org, security@kernel.org,
Zhitong Liu <liuzhitong1993@gmail.com>,
Qianchang Zhao <pioooooooooip@gmail.com>,
stable@vger.kernel.org
Subject: [PATCH] ksmbd: vfs: fix truncate lock-range check for shrink/grow and avoid size==0 underflow
Date: Sat, 8 Nov 2025 21:36:09 +0900 [thread overview]
Message-ID: <20251108123609.382365-1-pioooooooooip@gmail.com> (raw)
In-Reply-To: <2025110803-retrace-unnatural-127f@gregkh>
ksmbd_vfs_truncate() uses check_lock_range() with arguments that are
incorrect for shrink, and can underflow when size==0:
- For shrink, the code passed [inode->i_size, size-1], which is reversed.
- When size==0, "size-1" underflows to -1, so the range becomes
[old_size, -1], effectively skipping the intended [0, old_size-1].
Fix by:
- Rejecting negative size with -EINVAL.
- For shrink (size < old): check [size, old-1].
- For grow (size > old): check [old, size-1].
- Skip lock check when size == old.
- Keep the return value on conflict as -EAGAIN (no noisy pr_err()).
This avoids the size==0 underflow and uses the correct range order,
preserving byte-range lock semantics.
Reported-by: Qianchang Zhao <pioooooooooip@gmail.com>
Reported-by: Zhitong Liu <liuzhitong1993@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Qianchang Zhao <pioooooooooip@gmail.com>
---
fs/smb/server/vfs.c | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
index 891ed2dc2..e7843ec9b 100644
--- a/fs/smb/server/vfs.c
+++ b/fs/smb/server/vfs.c
@@ -825,17 +825,27 @@ int ksmbd_vfs_truncate(struct ksmbd_work *work,
if (!work->tcon->posix_extensions) {
struct inode *inode = file_inode(filp);
- if (size < inode->i_size) {
- err = check_lock_range(filp, size,
- inode->i_size - 1, WRITE);
- } else {
- err = check_lock_range(filp, inode->i_size,
- size - 1, WRITE);
+ loff_t old = i_size_read(inode);
+ loff_t start = 0, end = -1;
+ bool need_check = false;
+
+ if (size < 0)
+ return -EINVAL;
+
+ if (size < old) {
+ start = size;
+ end = old - 1;
+ need_check = true;
+ } else if (size > old) {
+ start = old;
+ end = size - 1;
+ need_check = true;
}
- if (err) {
- pr_err("failed due to lock\n");
- return -EAGAIN;
+ if (need_check) {
+ err = check_lock_range(filp, start, end, WRITE);
+ if (err)
+ return -EAGAIN;
}
}
--
2.34.1
next parent reply other threads:[~2025-11-08 12:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <2025110803-retrace-unnatural-127f@gregkh>
2025-11-08 12:36 ` Qianchang Zhao [this message]
2025-11-08 14:46 ` [PATCH] ksmbd: vfs: fix truncate lock-range check for shrink/grow and avoid size==0 underflow Namjae Jeon
2025-11-08 15:57 ` [PATCH v2] ksmbd: vfs: skip lock-range check on equal size to " Qianchang Zhao
2025-11-09 1:32 ` Namjae Jeon
2025-11-08 16:00 ` [PATCH] ksmbd: vfs: fix truncate lock-range check for shrink/grow and " くさあさ
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