Re: [PATCH v1] audit,module: restore audit logging in load failure case

[Paul Moore <paul@paul-moore.com>]

On Oct 23, 2024 Richard Guy Briggs <rgb@redhat.com> wrote:
> 
> The move of the module sanity check to earlier skipped the audit logging
> call in the case of failure and to a place where the previously used
> context is unavailable.
> 
> Add an audit logging call for the module loading failure case and get
> the module name when possible.
> 
> Link: https://issues.redhat.com/browse/RHEL-52839
> Fixes: 02da2cbab452 ("module: move check_modinfo() early to early_mod_check()")
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
>  kernel/module/main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 49b9bca9de12..1f482532ef66 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -3057,8 +3057,10 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	 * failures once the proper module was allocated and
>  	 * before that.
>  	 */
> -	if (!module_allocated)
> +	if (!module_allocated) {
> +		audit_log_kern_module(info->name ? info->name : "(unavailable)");
>  		mod_stat_bump_becoming(info, flags);
> +	}

We probably should move the existing audit_log_kern_module() to just
after the elf_validity_cache_copy() call as both info->name and
info->mod->name should be as valid as they are going to get at that
point.  If we do that then we only have two cases we need to worry about,
a failed module_sig_check() or a failed elf_validity_cache_copy(), and
in both cases we can use "(unavailable)" without having to check
info->name first.

However, assuming we move the audit_log_kern_module() call up a bit as
described above, I'm not sure there is much value in calling
audit_log_kern_module() with an "(unavailable)" module name in those
early two cases.  We know it's an attempted module load based on the
SYSCALL record, seeing an associated "(unavailable)" KERN_MODULE record
doesn't provide us with any more information than if we had simply
skipped the KERN_MODULE record.

Untested, but this is what I'm talking about:

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 0050ef288ab3..eaa10e3c7eca 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -417,7 +417,7 @@ extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm,
 extern void __audit_log_capset(const struct cred *new, const struct cred *old);
 extern void __audit_mmap_fd(int fd, int flags);
 extern void __audit_openat2_how(struct open_how *how);
-extern void __audit_log_kern_module(char *name);
+extern void __audit_log_kern_module(const char *name);
 extern void __audit_fanotify(u32 response, struct fanotify_response_info_audit_rule *friar);
 extern void __audit_tk_injoffset(struct timespec64 offset);
 extern void __audit_ntp_log(const struct audit_ntp_data *ad);
@@ -519,7 +519,7 @@ static inline void audit_openat2_how(struct open_how *how)
                __audit_openat2_how(how);
 }
 
-static inline void audit_log_kern_module(char *name)
+static inline void audit_log_kern_module(const char *name)
 {
        if (!audit_dummy_context())
                __audit_log_kern_module(name);
@@ -677,7 +677,7 @@ static inline void audit_mmap_fd(int fd, int flags)
 static inline void audit_openat2_how(struct open_how *how)
 { }
 
-static inline void audit_log_kern_module(char *name)
+static inline void audit_log_kern_module(const char *name)
 {
 }
 
diff --git a/kernel/audit.h b/kernel/audit.h
index a60d2840559e..5156ecd35457 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -199,7 +199,7 @@ struct audit_context {
                        int                     argc;
                } execve;
                struct {
-                       char                    *name;
+                       const char              *name;
                } module;
                struct {
                        struct audit_ntp_data   ntp_data;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 0627e74585ce..f79eb3a5a789 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2870,7 +2870,7 @@ void __audit_openat2_how(struct open_how *how)
        context->type = AUDIT_OPENAT2;
 }
 
-void __audit_log_kern_module(char *name)
+void __audit_log_kern_module(const char *name)
 {
        struct audit_context *context = audit_context();
 
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 49b9bca9de12..3acb65073c53 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2884,6 +2884,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
        if (err)
                goto free_copy;
 
+       audit_log_kern_module(info->name);
+
        err = early_mod_check(info, flags);
        if (err)
                goto free_copy;
@@ -2897,8 +2899,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
 
        module_allocated = true;
 
-       audit_log_kern_module(mod->name);
-
        /* Reserve our place in the list. */
        err = add_unformed_module(mod);
        if (err)

--
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