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audit: reduce mmap_sem hold for mm->exe_file

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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>
This commit is contained in:
Davidlohr Bueso 2015-02-22 18:20:09 -08:00 committed by Paul Moore
parent 4766b199ef
commit 5b28255278
1 changed files with 14 additions and 8 deletions
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22
kernel/audit.c
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@ -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;
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);
if (!mm)
goto out_null;
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)