On Wed 22-11-23 14:27:06, Amir Goldstein wrote:
> 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>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> 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
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
