audit: reduce mmap_sem hold for mm->exe_file (5b282552) · Commits · 戴 / test

The mm->exe_file is currently serialized with mmap_sem (shared) in order to both safely (1) read the file and (2) audit it via audit_log_d_path(). Good users will, on the other hand, make use of the more standard get_mm_exe_file(), requiring only holding the mmap_sem to read the value, and relying on reference counting to make sure that the exe file won't dissapear underneath us. Additionally, upon NULL return of get_mm_exe_file, we also call audit_log_format(ab, " exe=(null)"). Signed-off-by:

Davidlohr Bueso <dbueso@suse.de> [PM: tweaked subject line] Signed-off-by:

Paul Moore <pmoore@redhat.com>

kernel/audit.c

+14 −8

Original line number	Diff line number	Diff line
		@@ -43,6 +43,7 @@

		#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

		#include <linux/file.h>
		#include <linux/init.h>
		#include <linux/types.h>
		#include <linux/atomic.h>
		@@ -1851,15 +1852,20 @@ EXPORT_SYMBOL(audit_log_task_context);
		void audit_log_d_path_exe(struct audit_buffer *ab,
		struct mm_struct *mm)
		{
		if (!mm) {
		audit_log_format(ab, " exe=(null)");
		return;
		}
		struct file *exe_file;

		if (!mm)
		goto out_null;

		down_read(&mm->mmap_sem);
		if (mm->exe_file)
		audit_log_d_path(ab, " exe=", &mm->exe_file->f_path);
		up_read(&mm->mmap_sem);
		exe_file = get_mm_exe_file(mm);
		if (!exe_file)
		goto out_null;

		audit_log_d_path(ab, " exe=", &exe_file->f_path);
		fput(exe_file);
		return;
		out_null:
		audit_log_format(ab, " exe=(null)");
		}

		void audit_log_task_info(struct audit_buffer ab, struct task_struct tsk)

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