diff options
| author | Vivek Goyal <vgoyal@redhat.com> | 2016-07-13 11:00:14 -0400 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2016-07-29 12:05:24 +0200 |
| commit | 500cac3ccee65526d5075da3af2674101305bf8c (patch) | |
| tree | bf22531069f9cb4cce94431dc3aa28f4cbe5820d | |
| parent | e29841a0ab3d03e77313abd8fb4c16e80fb26e29 (diff) | |
| download | linux-500cac3ccee65526d5075da3af2674101305bf8c.tar.bz2 | |
ovl: append MAY_READ when diluting write checks
Right now we remove MAY_WRITE/MAY_APPEND bits from mask if realfile is on
lower/. This is done as files on lower will never be written and will be
copied up. But to copy up a file, mounter should have MAY_READ permission
otherwise copy up will fail. So set MAY_READ in mask when MAY_WRITE is
reset.
Dan Walsh noticed this when he did access(lowerfile, W_OK) and it returned
True (context mounts) but when he tried to actually write to file, it
failed as mounter did not have permission on lower file.
[SzM] don't set MAY_READ if only MAY_APPEND is set without MAY_WRITE; this
won't trigger a copy-up.
Reported-by: Dan Walsh <dwalsh@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
| -rw-r--r-- | fs/overlayfs/inode.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 76cfe9d04e64..1b885c156028 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -137,8 +137,11 @@ int ovl_permission(struct inode *inode, int mask) return err; old_cred = ovl_override_creds(inode->i_sb); - if (!is_upper && !special_file(realinode->i_mode)) + if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) { mask &= ~(MAY_WRITE | MAY_APPEND); + /* Make sure mounter can read file for copy up later */ + mask |= MAY_READ; + } err = inode_permission(realinode, mask); revert_creds(old_cred); |