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authorVivek Goyal <vgoyal@redhat.com>2016-07-13 11:00:14 -0400
committerMiklos Szeredi <mszeredi@redhat.com>2016-07-29 12:05:24 +0200
commit500cac3ccee65526d5075da3af2674101305bf8c (patch)
treebf22531069f9cb4cce94431dc3aa28f4cbe5820d /fs/overlayfs
parente29841a0ab3d03e77313abd8fb4c16e80fb26e29 (diff)
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>
Diffstat (limited to 'fs/overlayfs')
-rw-r--r--fs/overlayfs/inode.c5
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);