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remap_range: move file_start_write() to after permission hook

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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@toxicpanda.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231122122715.2561213-8-amir73il@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Amir Goldstein 2023-11-22 14:27:06 +02:00 • committed by Christian Brauner
parent dfad37051a
commit 0b5263d12a
1 changed files with 13 additions and 8 deletions
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21
fs/remap_range.c
View file

@ -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;