Re: [PATCH 1/2] audit: add support for the openat2 syscall

[+Cc Aleksa, the author of openat2()]

and a comment below. :)

On Wed, Mar 17, 2021 at 09:47:17PM -0400, Richard Guy Briggs wrote:

quoted

The openat2(2) syscall was added in kernel v5.6 with commit fddb5d430ad9
("open: introduce openat2(2) syscall")

Add the openat2(2) syscall to the audit syscall classifier.

See the github issue
https://github.com/linux-audit/audit-kernel/issues/67

Signed-off-by: Richard Guy Briggs <redacted>
---
 arch/alpha/kernel/audit.c          | 2 ++
 arch/ia64/kernel/audit.c           | 2 ++
 arch/parisc/kernel/audit.c         | 2 ++
 arch/parisc/kernel/compat_audit.c  | 2 ++
 arch/powerpc/kernel/audit.c        | 2 ++
 arch/powerpc/kernel/compat_audit.c | 2 ++
 arch/s390/kernel/audit.c           | 2 ++
 arch/s390/kernel/compat_audit.c    | 2 ++
 arch/sparc/kernel/audit.c          | 2 ++
 arch/sparc/kernel/compat_audit.c   | 2 ++
 arch/x86/ia32/audit.c              | 2 ++
 arch/x86/kernel/audit_64.c         | 2 ++
 kernel/auditsc.c                   | 3 +++
 lib/audit.c                        | 4 ++++
 lib/compat_audit.c                 | 4 ++++
 15 files changed, 35 insertions(+)

diff --git a/arch/alpha/kernel/audit.c b/arch/alpha/kernel/audit.c
index 96a9d18ff4c4..06a911b685d1 100644
--- a/arch/alpha/kernel/audit.c
+++ b/arch/alpha/kernel/audit.c

@@ -42,6 +42,8 @@ int audit_classify_syscall(int abi, unsigned syscall)
 		return 3;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/arch/ia64/kernel/audit.c b/arch/ia64/kernel/audit.c
index 5192ca899fe6..5eaa888c8fd3 100644
--- a/arch/ia64/kernel/audit.c
+++ b/arch/ia64/kernel/audit.c

@@ -43,6 +43,8 @@ int audit_classify_syscall(int abi, unsigned syscall)
 		return 3;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/arch/parisc/kernel/audit.c b/arch/parisc/kernel/audit.c
index 9eb47b2225d2..fc721a7727ba 100644
--- a/arch/parisc/kernel/audit.c
+++ b/arch/parisc/kernel/audit.c

@@ -52,6 +52,8 @@ int audit_classify_syscall(int abi, unsigned syscall)
 		return 3;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/arch/parisc/kernel/compat_audit.c b/arch/parisc/kernel/compat_audit.c
index 20c39c9d86a9..fc6d35918c44 100644
--- a/arch/parisc/kernel/compat_audit.c
+++ b/arch/parisc/kernel/compat_audit.c

@@ -35,6 +35,8 @@ int parisc32_classify_syscall(unsigned syscall)
 		return 3;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 1;
 	}

diff --git a/arch/powerpc/kernel/audit.c b/arch/powerpc/kernel/audit.c
index a2dddd7f3d09..8f32700b0baa 100644
--- a/arch/powerpc/kernel/audit.c
+++ b/arch/powerpc/kernel/audit.c

@@ -54,6 +54,8 @@ int audit_classify_syscall(int abi, unsigned syscall)
 		return 4;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/arch/powerpc/kernel/compat_audit.c b/arch/powerpc/kernel/compat_audit.c
index 55c6ccda0a85..ebe45534b1c9 100644
--- a/arch/powerpc/kernel/compat_audit.c
+++ b/arch/powerpc/kernel/compat_audit.c

@@ -38,6 +38,8 @@ int ppc32_classify_syscall(unsigned syscall)
 		return 4;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 1;
 	}

diff --git a/arch/s390/kernel/audit.c b/arch/s390/kernel/audit.c
index d395c6c9944c..d964cb94cfaf 100644
--- a/arch/s390/kernel/audit.c
+++ b/arch/s390/kernel/audit.c

@@ -54,6 +54,8 @@ int audit_classify_syscall(int abi, unsigned syscall)
 		return 4;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/arch/s390/kernel/compat_audit.c b/arch/s390/kernel/compat_audit.c
index 444fb1f66944..f7b32933ce0e 100644
--- a/arch/s390/kernel/compat_audit.c
+++ b/arch/s390/kernel/compat_audit.c

@@ -39,6 +39,8 @@ int s390_classify_syscall(unsigned syscall)
 		return 4;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 1;
 	}

diff --git a/arch/sparc/kernel/audit.c b/arch/sparc/kernel/audit.c
index a6e91bf34d48..b6dcca9c6520 100644
--- a/arch/sparc/kernel/audit.c
+++ b/arch/sparc/kernel/audit.c

@@ -55,6 +55,8 @@ int audit_classify_syscall(int abi, unsigned int syscall)
 		return 4;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/arch/sparc/kernel/compat_audit.c b/arch/sparc/kernel/compat_audit.c
index 10eeb4f15b20..d2652a1083ad 100644
--- a/arch/sparc/kernel/compat_audit.c
+++ b/arch/sparc/kernel/compat_audit.c

@@ -39,6 +39,8 @@ int sparc32_classify_syscall(unsigned int syscall)
 		return 4;
 	case __NR_execve:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 1;
 	}

diff --git a/arch/x86/ia32/audit.c b/arch/x86/ia32/audit.c
index 6efe6cb3768a..57a02ade5503 100644
--- a/arch/x86/ia32/audit.c
+++ b/arch/x86/ia32/audit.c

@@ -39,6 +39,8 @@ int ia32_classify_syscall(unsigned syscall)
 	case __NR_execve:
 	case __NR_execveat:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 1;
 	}

diff --git a/arch/x86/kernel/audit_64.c b/arch/x86/kernel/audit_64.c
index 83d9cad4e68b..39de1e021258 100644
--- a/arch/x86/kernel/audit_64.c
+++ b/arch/x86/kernel/audit_64.c

@@ -53,6 +53,8 @@ int audit_classify_syscall(int abi, unsigned syscall)
 	case __NR_execve:
 	case __NR_execveat:
 		return 5;
+	case __NR_openat2:
+		return 6;
 	default:
 		return 0;
 	}

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 8bb9ac84d2fb..f5616e70d129 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c

@@ -76,6 +76,7 @@
 #include <linux/fsnotify_backend.h>
 #include <uapi/linux/limits.h>
 #include <uapi/linux/netfilter/nf_tables.h>
+#include <uapi/linux/openat2.h>
 
 #include "audit.h"
 

@@ -195,6 +196,8 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
 		return ((mask & AUDIT_PERM_WRITE) && ctx->argv[0] == SYS_BIND);
 	case 5: /* execve */
 		return mask & AUDIT_PERM_EXEC;
+	case 6: /* openat2 */
+		return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);

That looks a bit dodgy. Maybe sm like the below would be a bit better?

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 47fb48f42c93..531e882a5096 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c

@@ -159,6 +159,7 @@ static const struct audit_nfcfgop_tab audit_nfcfgs[] = {

 static int audit_match_perm(struct audit_context *ctx, int mask)
 {
+       struct open_how *openat2;
        unsigned n;
        if (unlikely(!ctx))
                return 0;

@@ -195,6 +196,12 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
                return ((mask & AUDIT_PERM_WRITE) && ctx->argv[0] == SYS_BIND);
        case 5: /* execve */
                return mask & AUDIT_PERM_EXEC;
+       case 6: /* openat2 */
+               openat2 = ctx->argv[2];
+               if (upper_32_bits(openat2->flags))
+                       pr_warn("Some sensible warning about unknown flags");
+
+               return mask & ACC_MODE(lower_32_bits(openat2->flags));
        default:
                return 0;
        }

(Ideally we'd probably notice at build-time that we've got flags
exceeding 32bits. Could probably easily been done by exposing an all
flags macro somewhere and then we can place a BUILD_BUG_ON() or sm into
such places.)