Re: [PATCH v4 2/3] audit: add support for the openat2 syscall

From: Christian Brauner
Date: Thu May 20 2021 - 03:58:51 EST


On Wed, May 19, 2021 at 04:00:21PM -0400, Richard Guy Briggs wrote:
> 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.
>
> Link: https://github.com/linux-audit/audit-kernel/issues/67
> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/f5f1a4d8699613f8c02ce762807228c841c2e26f.1621363275.git.rgb@xxxxxxxxxx
> ---
> 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 ++
> include/linux/auditsc_classmacros.h | 1 +
> kernel/auditsc.c | 3 +++
> lib/audit.c | 4 ++++
> lib/compat_audit.c | 4 ++++
> 16 files changed, 36 insertions(+)
>
> diff --git a/arch/alpha/kernel/audit.c b/arch/alpha/kernel/audit.c
> index 81cbd804e375..3ab04709784a 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 AUDITSC_OPENAT;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/arch/ia64/kernel/audit.c b/arch/ia64/kernel/audit.c
> index dba6a74c9ab3..ec61f20ca61f 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 AUDITSC_OPENAT;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/arch/parisc/kernel/audit.c b/arch/parisc/kernel/audit.c
> index 14244e83db75..f420b5552140 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 AUDITSC_OPENAT;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/arch/parisc/kernel/compat_audit.c b/arch/parisc/kernel/compat_audit.c
> index 1d6347d37d92..3ec490c28656 100644
> --- a/arch/parisc/kernel/compat_audit.c
> +++ b/arch/parisc/kernel/compat_audit.c
> @@ -36,6 +36,8 @@ int parisc32_classify_syscall(unsigned syscall)
> return AUDITSC_OPENAT;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_COMPAT;
> }
> diff --git a/arch/powerpc/kernel/audit.c b/arch/powerpc/kernel/audit.c
> index 6eb18ef77dff..1bcfca5fdf67 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 AUDITSC_SOCKETCALL;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/arch/powerpc/kernel/compat_audit.c b/arch/powerpc/kernel/compat_audit.c
> index b1dc2d1c4bad..251abf79d536 100644
> --- a/arch/powerpc/kernel/compat_audit.c
> +++ b/arch/powerpc/kernel/compat_audit.c
> @@ -39,6 +39,8 @@ int ppc32_classify_syscall(unsigned syscall)
> return AUDITSC_SOCKETCALL;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_COMPAT;
> }
> diff --git a/arch/s390/kernel/audit.c b/arch/s390/kernel/audit.c
> index 7e331e1831d4..02051a596b87 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 AUDITSC_SOCKETCALL;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/arch/s390/kernel/compat_audit.c b/arch/s390/kernel/compat_audit.c
> index fc3d1c7ad21c..4b3d463e7d97 100644
> --- a/arch/s390/kernel/compat_audit.c
> +++ b/arch/s390/kernel/compat_audit.c
> @@ -40,6 +40,8 @@ int s390_classify_syscall(unsigned syscall)
> return AUDITSC_SOCKETCALL;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_COMPAT;
> }
> diff --git a/arch/sparc/kernel/audit.c b/arch/sparc/kernel/audit.c
> index 50fab35bdaba..b092274eca79 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 AUDITSC_SOCKETCALL;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/arch/sparc/kernel/compat_audit.c b/arch/sparc/kernel/compat_audit.c
> index 1c1b6d075421..2a3f71206fc5 100644
> --- a/arch/sparc/kernel/compat_audit.c
> +++ b/arch/sparc/kernel/compat_audit.c
> @@ -40,6 +40,8 @@ int sparc32_classify_syscall(unsigned int syscall)
> return AUDITSC_SOCKETCALL;
> case __NR_execve:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_COMPAT;
> }
> diff --git a/arch/x86/ia32/audit.c b/arch/x86/ia32/audit.c
> index eedc37a1ee13..efc7d832fefb 100644
> --- a/arch/x86/ia32/audit.c
> +++ b/arch/x86/ia32/audit.c
> @@ -40,6 +40,8 @@ int ia32_classify_syscall(unsigned syscall)
> case __NR_execve:
> case __NR_execveat:
> return AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_COMPAT;
> }
> diff --git a/arch/x86/kernel/audit_64.c b/arch/x86/kernel/audit_64.c
> index 2a6cc9c9c881..44c3601cfdc4 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 AUDITSC_EXECVE;
> + case __NR_openat2:
> + return AUDITSC_OPENAT2;
> default:
> return AUDITSC_NATIVE;
> }
> diff --git a/include/linux/auditsc_classmacros.h b/include/linux/auditsc_classmacros.h
> index 18757d270961..dc8e72536dbd 100644
> --- a/include/linux/auditsc_classmacros.h
> +++ b/include/linux/auditsc_classmacros.h
> @@ -16,6 +16,7 @@ enum auditsc_class_t {
> AUDITSC_OPENAT,
> AUDITSC_SOCKETCALL,
> AUDITSC_EXECVE,
> + AUDITSC_OPENAT2,
>
> AUDITSC_NVALS /* count */
> };
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index d775ea16505b..3f59ab209dfd 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"
>
> @@ -196,6 +197,8 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
> return ((mask & AUDIT_PERM_WRITE) && ctx->argv[0] == SYS_BIND);
> case AUDITSC_EXECVE:
> return mask & AUDIT_PERM_EXEC;
> + case AUDITSC_OPENAT2:
> + return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);

That's a lot of dereferncing, casting and masking all at once. Maybe a
small static inline helper would be good for the sake of legibility? Sm
like:

static inline u32 audit_openat2_acc(struct open_how *how, int mask)
{
u32 flags = how->flags;
return mask & ACC_MODE(flags);
}

but not sure. Just seems more legible to me.
Otherwise.
Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>