In vfs code, file_start_write() is usually called after the permission
hook in rw_verify_area(). vfs_dedupe_file_range_one() is an exception
to this rule.
In vfs_dedupe_file_range_one(), move file_start_write() to after the
the rw_verify_area() checks to make them "start-write-safe".
This is needed for fanotify "pre content" events.
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/remap_range.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/fs/remap_range.c b/fs/remap_range.c
index 42f79cb2b1b1..12131f2a6c9e 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -420,7 +420,7 @@ loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
EXPORT_SYMBOL(vfs_clone_file_range);
/* Check whether we are allowed to dedupe the destination file */
-static bool allow_file_dedupe(struct file *file)
+static bool may_dedupe_file(struct file *file)
{
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct inode *inode = file_inode(file);
@@ -445,24 +445,29 @@ loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
WARN_ON_ONCE(remap_flags & ~(REMAP_FILE_DEDUP |
REMAP_FILE_CAN_SHORTEN));
- ret = mnt_want_write_file(dst_file);
- if (ret)
- return ret;
-
/*
* This is redundant if called from vfs_dedupe_file_range(), but other
* callers need it and it's not performance sesitive...
*/
ret = remap_verify_area(src_file, src_pos, len, false);
if (ret)
- goto out_drop_write;
+ return ret;
ret = remap_verify_area(dst_file, dst_pos, len, true);
if (ret)
- goto out_drop_write;
+ return ret;
+
+ /*
+ * This needs to be called after remap_verify_area() because of
+ * sb_start_write() and before may_dedupe_file() because the mount's
+ * MAY_WRITE need to be checked with mnt_get_write_access_file() held.
+ */
+ ret = mnt_want_write_file(dst_file);
+ if (ret)
+ return ret;
ret = -EPERM;
- if (!allow_file_dedupe(dst_file))
+ if (!may_dedupe_file(dst_file))
goto out_drop_write;
ret = -EXDEV;
--
2.34.1
