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btrfs: fix fallocate to use file_modified to update permissions consistently

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[ Upstream commit 05fd9564e9faf0f23b4676385e27d9405cef6637 ]

Since the initial introduction of (posix) fallocate back at the turn of
the century, it has been possible to use this syscall to change the
user-visible contents of files.  This can happen by extending the file
size during a preallocation, or through any of the newer modes (punch,
zero range).  Because the call can be used to change file contents, we
should treat it like we do any other modification to a file -- update
the mtime, and drop set[ug]id privileges/capabilities.

The VFS function file_modified() does all this for us if pass it a
locked inode, so let's make fallocate drop permissions correctly.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Darrick J. Wong
2022-03-14 10:55:32 -07:00
committed by Greg Kroah-Hartman
parent 9b5d1b3413
commit 217190dc66
1 changed files with 11 additions and 2 deletions
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13
fs/btrfs/file.c
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@@ -2833,8 +2833,9 @@ out:
return ret; return ret;
} }
static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len) static int btrfs_punch_hole(struct file *file, loff_t offset, loff_t len)
{ {
struct inode *inode = file_inode(file);
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
struct btrfs_root *root = BTRFS_I(inode)->root; struct btrfs_root *root = BTRFS_I(inode)->root;
struct extent_state *cached_state = NULL; struct extent_state *cached_state = NULL;
@@ -2866,6 +2867,10 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
goto out_only_mutex; goto out_only_mutex;
} }
ret = file_modified(file);
if (ret)
goto out_only_mutex;
lockstart = round_up(offset, btrfs_inode_sectorsize(BTRFS_I(inode))); lockstart = round_up(offset, btrfs_inode_sectorsize(BTRFS_I(inode)));
lockend = round_down(offset + len, lockend = round_down(offset + len,
btrfs_inode_sectorsize(BTRFS_I(inode))) - 1; btrfs_inode_sectorsize(BTRFS_I(inode))) - 1;
@@ -3301,7 +3306,7 @@ static long btrfs_fallocate(struct file *file, int mode,
return -EOPNOTSUPP; return -EOPNOTSUPP;
if (mode & FALLOC_FL_PUNCH_HOLE) if (mode & FALLOC_FL_PUNCH_HOLE)
return btrfs_punch_hole(inode, offset, len); return btrfs_punch_hole(file, offset, len);
/* /*
* Only trigger disk allocation, don't trigger qgroup reserve * Only trigger disk allocation, don't trigger qgroup reserve
@@ -3323,6 +3328,10 @@ static long btrfs_fallocate(struct file *file, int mode,
goto out; goto out;
} }
ret = file_modified(file);
if (ret)
goto out;
/* /*
* TODO: Move these two operations after we have checked * TODO: Move these two operations after we have checked
* accurate reserved space, or fallocate can still fail but * accurate reserved space, or fallocate can still fail but