audit: fix suffixed '/' filename matching

When the user specifies a directory to delete with the suffix '/',
the audit record fails to collect the filename, resulting in the
following logs:

 type=PATH msg=audit(10/30/2024 14:11:17.796:6304) : item=2 name=(null)
 type=PATH msg=audit(10/30/2024 14:11:17.796:6304) : item=1 name=(null)

It happens because the value of the variables dname, and n->name->name
in __audit_inode_child() differ only by the suffix '/'. This commit
treats this corner case by handling pathname's trailing slashes in
audit_compare_dname_path().

Steps to reproduce the issue:

 # auditctl -w /tmp
 $ mkdir /tmp/foo
 $ rm -r /tmp/foo/
 # ausearch -i | grep PATH | tail -3

The first version of this patch was based on a GitHub patch/PR by
user @hqh2010 [1].

Link: https://github.com/linux-audit/audit-kernel/pull/148
Suggested-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
[PM: subject tweak, trim old metadata]
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index bceb9f58a09ee709217ab082c2eddf9da15e0adc..e3f42018ed46fa7cc31d5aeb9b5a3b11a9c03cae 100644 (file)
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -1319,13 +1319,20 @@ int audit_compare_dname_path(const struct qstr *dname, const char *path, int par
        if (pathlen < dlen)
                return 1;
 
-       parentlen = parentlen == AUDIT_NAME_FULL ? parent_len(path) : parentlen;
-       if (pathlen - parentlen != dlen)
-               return 1;
+       if (parentlen == AUDIT_NAME_FULL)
+               parentlen = parent_len(path);
 
        p = path + parentlen;
 
-       return strncmp(p, dname->name, dlen);
+       /* handle trailing slashes */
+       pathlen -= parentlen;
+       while (p[pathlen - 1] == '/')
+               pathlen--;
+
+       if (pathlen != dlen)
+               return 1;
+
+       return memcmp(p, dname->name, dlen);
 }
 
 int audit_filter(int msgtype, unsigned int listtype)