The user pointer was being illegally dereferenced directly to get the
open_how flags data in audit_match_perm.  Use the previously saved flags
data elsewhere in the context instead.

Coverage is provided by the audit-testsuite syscalls_file test case.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/c96031b4-b76d-d82c-e232-1cccbbf71946@suse.com
Fixes: 1c30e3af8a79 ("audit: add support for the openat2 syscall")
Reported-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
 kernel/auditsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index fce5d43a933f..81ab510a7be4 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -185,7 +185,7 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
 	case AUDITSC_EXECVE:
 		return mask & AUDIT_PERM_EXEC;
 	case AUDITSC_OPENAT2:
-		return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);
+		return mask & ACC_MODE((u32)(ctx->openat2.flags));
 	default:
 		return 0;
 	}
-- 
2.27.0

On Wed, Feb 9, 2022 at 4:51 PM Richard Guy Briggs <rgb@redhat.com> wrote:
>
> The user pointer was being illegally dereferenced directly to get the
> open_how flags data in audit_match_perm.  Use the previously saved flags
> data elsewhere in the context instead.
>
> Coverage is provided by the audit-testsuite syscalls_file test case.
>
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/r/c96031b4-b76d-d82c-e232-1cccbbf71946@suse.com
> Fixes: 1c30e3af8a79 ("audit: add support for the openat2 syscall")
> Reported-by: Jeff Mahoney <jeffm@suse.com>
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
>  kernel/auditsc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks Richard.  As this came in ~40m after the other patch, and both
are identical code changes, I've merged the other patch but I did add
a note that you also submitted a similar patch.  Once the automated
testing completes I'll send this up to Linus.

-- 
paul-moore.com