From: Christian Brauner brauner@kernel.org
commit 2d8ae8c417db284f598dffb178cc01e7db0f1821 upstream.
We've aligned setgid behavior over multiple kernel releases. The details can be found in commit cf619f891971 ("Merge tag 'fs.ovl.setgid.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping") and commit 426b4ca2d6a5 ("Merge tag 'fs.setgid.v6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux"). Consistent setgid stripping behavior is now encapsulated in the setattr_should_drop_sgid() helper which is used by all filesystems that strip setgid bits outside of vfs proper. Usually ATTR_KILL_SGID is raised in e.g., chown_common() and is subject to the setattr_should_drop_sgid() check to determine whether the setgid bit can be retained. Since nfsd is raising ATTR_KILL_SGID unconditionally it will cause notify_change() to strip it even if the caller had the necessary privileges to retain it. Ensure that nfsd only raises ATR_KILL_SGID if the caller lacks the necessary privileges to retain the setgid bit.
Without this patch the setgid stripping tests in LTP will fail:
As you can see, the problem is S_ISGID (0002000) was dropped on a non-group-executable file while chown was invoked by super-user, while
[...]
fchown02.c:66: TFAIL: testfile2: wrong mode permissions 0100700, expected 0102700
[...]
chown02.c:57: TFAIL: testfile2: wrong mode permissions 0100700, expected 0102700
With this patch all tests pass.
Reported-by: Sherry Yang sherry.yang@oracle.com Signed-off-by: Christian Brauner brauner@kernel.org Reviewed-by: Jeff Layton jlayton@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com [Harshit: backport to 5.15.y: Use init_user_ns instead of nop_mnt_idmap as we don't have commit abf08576afe3 ("fs: port vfs_*() helpers to struct mnt_idmap")] Signed-off-by: Harshit Mogalapalli harshit.m.mogalapalli@oracle.com --- fs/nfsd/vfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index d4adc599737d..15a86876e3d9 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -322,7 +322,9 @@ nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap) iap->ia_mode &= ~S_ISGID; } else { /* set ATTR_KILL_* bits and let VFS handle it */ - iap->ia_valid |= (ATTR_KILL_SUID | ATTR_KILL_SGID); + iap->ia_valid |= ATTR_KILL_SUID; + iap->ia_valid |= + setattr_should_drop_sgid(&init_user_ns, inode); } } }