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List:       linux-audit
Subject:    Re: AUDIT_AVC_PATH problems
From:       Stephen Smalley <sds () tycho ! nsa ! gov>
Date:       2007-05-29 18:33:36
Message-ID: 1180463616.3340.133.camel () moss-spartans ! epoch ! ncsc ! mil
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On Tue, 2007-05-29 at 10:53 -0400, Alexander Viro wrote:
> 	Selinux folks had been complaining about the lack of AVC_PATH
> records when audit is disabled.  I must admit my stupidity - I assumed
> that avc_audit() really couldn't use audit_log_d_path() because of
> deadlocks (== could be called with dcache_lock or vfsmount_lock held).
> Shouldn't have made that assumption - it never gets called that way.
> It _is_ called under spinlocks, but not those.
> 
> 	Since audit_log_d_path() uses ab->gfp_mask for allocations, kmalloc()
> in there is not a problem.  IOW, the simple fix should be sufficient: let's
> rip AUDIT_AVC_PATH out and simply generate pathname as part of main record.
> It's trivial to do.  Patch below is against the mainline, rhel5 variant
> is also trivial.
> 
> 	Comments?
> 
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index fccc6e5..f3d6e5f 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -399,7 +399,6 @@ extern int audit_bprm(struct linux_binprm *bprm);
> extern int audit_socketcall(int nargs, unsigned long *args);
> extern int audit_sockaddr(int len, void *addr);
> extern int __audit_fd_pair(int fd1, int fd2);
> -extern int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt);
> extern int audit_set_macxattr(const char *name);
> extern int __audit_mq_open(int oflag, mode_t mode, struct mq_attr __user *u_attr);
> extern int __audit_mq_timedsend(mqd_t mqdes, size_t msg_len, unsigned int msg_prio, \
> const struct timespec __user *u_abs_timeout); @@ -479,7 +478,6 @@ extern int \
> audit_signals; #define audit_socketcall(n,a) ({ 0; })
> #define audit_fd_pair(n,a) ({ 0; })
> #define audit_sockaddr(len, addr) ({ 0; })
> -#define audit_avc_path(dentry, mnt) ({ 0; })
> #define audit_set_macxattr(n) do { ; } while (0)
> #define audit_mq_open(o,m,a) ({ 0; })
> #define audit_mq_timedsend(d,l,p,t) ({ 0; })
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index e36481e..10e0e6e 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -176,12 +176,6 @@ struct audit_aux_data_fd_pair {
> 	int	fd[2];
> };
> 
> -struct audit_aux_data_path {
> -	struct audit_aux_data	d;
> -	struct dentry		*dentry;
> -	struct vfsmount		*mnt;
> -};
> -
> struct audit_aux_data_pids {
> 	struct audit_aux_data	d;
> 	pid_t			target_pid[AUDIT_AUX_PIDS];
> @@ -657,12 +651,6 @@ static inline void audit_free_aux(struct audit_context \
> *context)  struct audit_aux_data *aux;
> 
> 	while ((aux = context->aux)) {
> -		if (aux->type == AUDIT_AVC_PATH) {
> -			struct audit_aux_data_path *axi = (void *)aux;
> -			dput(axi->dentry);
> -			mntput(axi->mnt);
> -		}
> -
> 		context->aux = aux->next;
> 		kfree(aux);
> 	}
> @@ -998,11 +986,6 @@ static void audit_log_exit(struct audit_context *context, \
> struct task_struct *ts  audit_log_hex(ab, axs->a, axs->len);
> 			break; }
> 
> -		case AUDIT_AVC_PATH: {
> -			struct audit_aux_data_path *axi = (void *)aux;
> -			audit_log_d_path(ab, "path=", axi->dentry, axi->mnt);
> -			break; }
> -
> 		case AUDIT_FD_PAIR: {
> 			struct audit_aux_data_fd_pair *axs = (void *)aux;
> 			audit_log_format(ab, "fd0=%d fd1=%d", axs->fd[0], axs->fd[1]);
> @@ -1952,36 +1935,6 @@ void __audit_ptrace(struct task_struct *t)
> }
> 
> /**
> - * audit_avc_path - record the granting or denial of permissions
> - * @dentry: dentry to record
> - * @mnt: mnt to record
> - *
> - * Returns 0 for success or NULL context or < 0 on error.
> - *
> - * Called from security/selinux/avc.c::avc_audit()
> - */
> -int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt)
> -{
> -	struct audit_aux_data_path *ax;
> -	struct audit_context *context = current->audit_context;
> -
> -	if (likely(!context))
> -		return 0;
> -
> -	ax = kmalloc(sizeof(*ax), GFP_ATOMIC);
> -	if (!ax)
> -		return -ENOMEM;
> -
> -	ax->dentry = dget(dentry);
> -	ax->mnt = mntget(mnt);
> -
> -	ax->d.type = AUDIT_AVC_PATH;
> -	ax->d.next = context->aux;
> -	context->aux = (void *)ax;
> -	return 0;
> -}
> -
> -/**
> * audit_signal_info - record signal info for shutting down audit subsystem
> * @sig: signal value
> * @t: task being signaled
> diff --git a/security/selinux/avc.c b/security/selinux/avc.c
> index e4396a8..2f4c2bb 100644
> --- a/security/selinux/avc.c
> +++ b/security/selinux/avc.c
> @@ -570,10 +570,12 @@ void avc_audit(u32 ssid, u32 tsid,
> 		case AVC_AUDIT_DATA_FS:
> 			if (a->u.fs.dentry) {
> 				struct dentry *dentry = a->u.fs.dentry;
> -				if (a->u.fs.mnt)
> -					audit_avc_path(dentry, a->u.fs.mnt);
> -				audit_log_format(ab, " name=");
> -				audit_log_untrustedstring(ab, dentry->d_name.name);
> +				if (a->u.fs.mnt) {
> +					audit_log_d_path(ab, "path=", dentry, a->u.fs.mnt);
> +				} else {
> +					audit_log_format(ab, " name=");
> +					audit_log_untrustedstring(ab, dentry->d_name.name);
> +				}
> 				inode = dentry->d_inode;
> 			} else if (a->u.fs.inode) {
> 				struct dentry *dentry;
> @@ -624,9 +626,8 @@ void avc_audit(u32 ssid, u32 tsid,
> 				case AF_UNIX:
> 					u = unix_sk(sk);
> 					if (u->dentry) {
> -						audit_avc_path(u->dentry, u->mnt);
> -						audit_log_format(ab, " name=");
> -						audit_log_untrustedstring(ab, u->dentry->d_name.name);
> +						audit_log_d_path(ab, "path=",
> +								 u->dentry, u->mnt);
> 						break;
> 					}
> 					if (!u->addr)
> 

Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>

-- 
Stephen Smalley
National Security Agency


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