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audit: fix exe_file access in audit_exe_compare
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Prior to the change the function would blindly deference mm, exe_file
and exe_file->f_inode, each of which could have been NULL or freed.

Use get_task_exe_file to safely obtain stable exe_file.

Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Acked-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Cc: <stable@vger.kernel.org> # 4.3.x
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Mateusz Guzik authored and Paul Moore committed Aug 31, 2016
1 parent cd81a91 commit 5efc244
Showing 1 changed file with 5 additions and 3 deletions.
8 changes: 5 additions & 3 deletions kernel/audit_watch.c
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/

#include <linux/file.h>
#include <linux/kernel.h>
#include <linux/audit.h>
#include <linux/kthread.h>
Expand Down Expand Up @@ -544,10 +545,11 @@ int audit_exe_compare(struct task_struct *tsk, struct audit_fsnotify_mark *mark)
unsigned long ino;
dev_t dev;

rcu_read_lock();
exe_file = rcu_dereference(tsk->mm->exe_file);
exe_file = get_task_exe_file(tsk);
if (!exe_file)
return 0;
ino = exe_file->f_inode->i_ino;
dev = exe_file->f_inode->i_sb->s_dev;
rcu_read_unlock();
fput(exe_file);
return audit_mark_compare(mark, ino, dev);
}

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