tree 3c4672de8e05a5f0a89b9be282505acc2948bbaf
parent 28e1d276157cb97e538ef9c7ff77f0f0f0b7bd93
author Stefan Berger <stefanb@linux.ibm.com> 1696251453 -0400
committer COS Cherry Picker <cloud-image-release@prod.google.com> 1702957028 -0800

fs: Pass AT_GETATTR_NOSEC flag to getattr interface function

Commit 8a924db2d7b5eb69ba08b1a0af46e9f1359a9bdf upstream.

When vfs_getattr_nosec() calls a filesystem's getattr interface function
then the 'nosec' should propagate into this function so that
vfs_getattr_nosec() can again be called from the filesystem's gettattr
rather than vfs_getattr(). The latter would add unnecessary security
checks that the initial vfs_getattr_nosec() call wanted to avoid.
Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass
with the new getattr_flags parameter to the getattr interface function.
In overlayfs and ecryptfs use this flag to determine which one of the
two functions to call.

In a recent code change introduced to IMA vfs_getattr_nosec() ended up
calling vfs_getattr() in overlayfs, which in turn called
security_inode_getattr() on an exiting process that did not have
current->fs set anymore, which then caused a kernel NULL pointer
dereference. With this change the call to security_inode_getattr() can
be avoided, thus avoiding the NULL pointer dereference.

BUG=b/314212897
TEST=presubmit
RELEASE_NOTE=None

cos-patch: bug
Reported-by: <syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com>
Fixes: db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Tyler Hicks <code@tyhicks.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Suggested-by: Christian Brauner <brauner@kernel.org>
Co-developed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Link: https://lore.kernel.org/r/20231002125733.1251467-1-stefanb@linux.vnet.ibm.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
(cherry picked from commit 8a924db2d7b5eb69ba08b1a0af46e9f1359a9bdf)
Signed-off-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Change-Id: I83a788b630f6ad5d49de03cf4614ffa6ccf55355
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/62556
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>