On Wed, Aug 03, 2016 at 09:45:06AM +0200, Greg Kroah-Hartman wrote:

On Wed, Aug 03, 2016 at 03:36:44PM +0800, Eryu Guan wrote:

quoted

On Mon, Jul 25, 2016 at 01:56:28PM -0700, Greg Kroah-Hartman wrote:

quoted

4.4-stable review patch.  If anyone has any objections, please let me know.

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From: Vivek Goyal <vgoyal@redhat.com>

commit 07a2daab49c549a37b5b744cbebb6e3f445f12bc upstream.

Right now when a new overlay inode is created, we initialize overlay
inode's ->i_mode from underlying inode ->i_mode but we retain only
file type bits (S_IFMT) and discard permission bits.

This patch changes it and retains permission bits too. This should allow
overlay to do permission checks on overlay inode itself in task context.

[SzM] It also fixes clearing suid/sgid bits on write.

This patch introduced a hang when writing to suid file, fstests
generic/355 could reproduce the hang easily, it only failed the test
without this patch and didn't hang the kernel.

Should we skip it for now and wait for a further fix?

Does Linus's tree have the same problem?

Yes, 4.7 kernel hangs as well.

quoted

(The 4.6-stable tree faces the same question)

Are we just missing a patch to be applied here?

AFAICT, no patch is available to fix it yet. But I've reported the bug
to Miklos (in RH bugzilla).

And this is already in the released stable kernels...

This patch is not in 4.7-rc7, it first appears in 4.7 kernel, seems like
the soak time is not long enough to let testings finish :) I finished my
4.7 kernel testing and identified the culprit this Monday.

Thanks,
Eryu