[PATCH 1/2] ubifs: fix FS_IOC_SETFLAGS unexpectedly clearing encrypt flag

[PATCH 1/2] ubifs: fix FS_IOC_SETFLAGS unexpectedly clearing encrypt flag

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

UBIFS's implementation of FS_IOC_SETFLAGS fails to preserve existing
inode flags that aren't settable by FS_IOC_SETFLAGS, namely the encrypt
flag.  This causes the encrypt flag to be unexpectedly cleared.

Fix it by preserving existing unsettable flags, like ext4 and f2fs do.

Test case with kvm-xfstests shell:

    FSTYP=ubifs KEYCTL_PROG=keyctl
    . fs/ubifs/config
    . ~/xfstests/common/encrypt
    dev=$(__blkdev_to_ubi_volume /dev/vdc)
    ubiupdatevol -t $dev
    mount $dev /mnt -t ubifs
    k=$(_generate_session_encryption_key)
    mkdir /mnt/edir
    xfs_io -c "set_encpolicy $k" /mnt/edir
    echo contents > /mnt/edir/file
    chattr +i /mnt/edir/file
    chattr -i /mnt/edir/file

With the bug, the following errors occur on the last command:

    [   18.081559] fscrypt (ubifs, inode 67): Inconsistent encryption context (parent directory: 65)
    chattr: Operation not permitted while reading flags on /mnt/edir/file

Fixes: d475a507457b ("ubifs: Add skeleton for fscrypto")
Cc: <stable@vger.kernel.org> # v4.10+
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/ubifs/ioctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ubifs/ioctl.c b/fs/ubifs/ioctl.c
index 5dc5abca11c70..eeb1be2598881 100644
--- a/fs/ubifs/ioctl.c
+++ b/fs/ubifs/ioctl.c
@@ -113,7 +113,8 @@ static int setflags(struct inode *inode, int flags)
 	if (err)
 		goto out_unlock;
 
-	ui->flags = ioctl2ubifs(flags);
+	ui->flags &= ~ioctl2ubifs(UBIFS_SUPPORTED_IOCTL_FLAGS);
+	ui->flags |= ioctl2ubifs(flags);
 	ubifs_set_inode_flags(inode);
 	inode->i_ctime = current_time(inode);
 	release = ui->dirty;
-- 
2.24.0.393.g34dc348eaf-goog

Re: [PATCH 1/2] ubifs: fix FS_IOC_SETFLAGS unexpectedly clearing encrypt flag

[Eric Biggers]

On Mon, Dec 16, 2019 at 03:06:35PM +0000, Sasha Levin wrote:
> Hi,
> 
> [This is an automated email]
> 
> This commit has been processed because it contains a "Fixes:" tag,
> fixing commit: d475a507457b ("ubifs: Add skeleton for fscrypto").
> 
> The bot has tested the following trees: v5.4.2, v5.3.15, v4.19.88, v4.14.158.
> 
> v5.4.2: Build OK!
> v5.3.15: Build OK!
> v4.19.88: Build failed! Errors:
>     fs/ubifs/ioctl.c:130:28: error: ‘UBIFS_SUPPORTED_IOCTL_FLAGS’ undeclared (first use in this function)
> 
> v4.14.158: Build failed! Errors:
>     fs/ubifs/ioctl.c:127:28: error: ‘UBIFS_SUPPORTED_IOCTL_FLAGS’ undeclared (first use in this function)
> 
> 
> NOTE: The patch will not be queued to stable trees until it is upstream.
> 
> How should we proceed with this patch?
> 

4.19 and 4.14 will build if you apply commit 2fe8b2d5578d
("ubifs: Reject unsupported ioctl flags explicitly") first.
That was a bug fix too, so I recommend applying it.

- Eric