On 11/17/2022 2:03 PM, Mimi Zohar wrote:
Hi Roberto,
On Thu, 2022-11-10 at 10:46 +0100, Roberto Sassu wrote:
From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Rewrite security_old_inode_init_security() to call
security_inode_init_security() before making changes to support multiple
LSMs providing xattrs. Do it so that the required changes are done only in
one place.
Only security_inode_init_security() has support for EVM. Making
security_old_inode_init_security() a wrapper for
security_inode_init_security() could result in security.evm extended
attributes being created that previously weren't created.
Hi Mimi
yes, I thought about this problem. In fact, it should not matter too
much. Since security_old_inode_init_security() supports setting only one
xattr: if there is an LSM xattr, that one will be set, and the EVM one
will be discarded; if there is no LSM xattr, EVM would not add one.
In fact ocfs2 defines ocfs2_init_security_get() as a wrapper for both
the old and new inode_init_security calls based on the caller's
preference. Only mknod and symlink seem to use the old function.
Wondering why do they differentiate between callers? (Cc'ing the ocfs2
mailing list as they're affected by this change.)
"[PATCH v4 1/5] reiserfs: Add missing calls to
reiserfs_security_free()" fixed a memory leak. I couldn't tell if
there was a similar memory leak in ocfs2, the only other user of
security_old_inode_init_security().
Will look into it.
As ocfs2 already defines initxattrs, that leaves only reiserfs missing
initxattrs(). A better, cleaner solution would be to define one.
Yes, great idea!
Thanks
Roberto
thanks,
Mimi
Define the security_initxattrs() callback and pass it to
security_inode_init_security() as argument, to obtain the first xattr
provided by LSMs.
This behavior is a bit different from the current one. Before this patch
calling call_int_hook() could cause multiple LSMs to provide an xattr,
since call_int_hook() does not stop when an LSM returns zero. The caller of
security_old_inode_init_security() receives the last xattr set. The pointer
of the xattr value of previous LSMs is lost, causing memory leaks.
However, in practice, this scenario does not happen as the only in-tree
LSMs providing an xattr at inode creation time are SELinux and Smack, which
are mutually exclusive.
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>b
