On 10/7/19 9:17 AM, Greg Kroah-Hartman wrote:
On Mon, Oct 07, 2019 at 06:16:16PM +0200, Greg Kroah-Hartman wrote:
On Mon, Oct 07, 2019 at 09:09:16AM -0700, Mark Salyzyn wrote:
When filtering xattr list for reading, presence of trusted xattr
results in a security audit log. However, if there is other content
no errno will be set, and if there isn't, the errno will be -ENODATA
and not -EPERM as is usually associated with a lack of capability.
The check does not block the request to list the xattrs present.
Switch to has_capability_noaudit to reflect a more appropriate check.
Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
Cc: linux-security-module@xxxxxxxxxxxxxxx
Cc: kernel-team@xxxxxxxxxxx
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v3.18
Fixes: upstream a082c6f680da ("ovl: filter trusted xattr for non-admin")
Fixes: 3.18 4bcc9b4b3a0a ("ovl: filter trusted xattr for non-admin")
---
Replaced ns_capable_noaudit with 3.18.y tree specific
has_capability_noaudit present in original submission to kernel.org
commit 5c2e9f346b815841f9bed6029ebcb06415caf640
("ovl: filter of trusted xattr results in audit")
fs/overlayfs/inode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index a01ec1836a72..1175efa5e956 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -265,7 +265,8 @@ static bool ovl_can_list(const char *s)
return true;
/* Never list trusted.overlay, list other trusted for superuser only */
- return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
+ return !ovl_is_private_xattr(s) &&
+ has_capability_noaudit(current, CAP_SYS_ADMIN);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
--
2.23.0.581.g78d2f28ef7-goog
Thanks for the backport, this one worked!
I spoke too soon:
ERROR: "has_capability_noaudit" [fs/overlayfs/overlay.ko] undefined!
That function isn't exported for modules :(
greg k-h
<sigh>
Now what is the playbook, we have three options in order of preference:
1) #ifdef MODULE use capable() to preserve API, add a short comment
about the side effects if overlayfs is used as a module.
2) export has_capability_nodaudit (proc and oom_kill use it, and are
both built-in only), but affect the 3.18 API at near EOL. AFAIK no one
wants that?
3) Do nothing more. Make this a distro concern only. Leave this posted
as a back-port for the record, but never merged, for those that are
_interested_ and declare 3.18 stable as noisy for sepolicy and overlayfs
under some usage patterns with few user space mitigation unless they
explicitly take this back-port into their tree (eg: android common
kernel) if used built-in. This way, in 3.18.y at least the module and
built-in version behave the _same_ in stable.
Looking for feedback.
Sincerely -- Mark Salyzyn
