[PATCH] xacct_add_tsk: fix pure theoretical ->mm use-after-free
Paranoid fix. The task can free its ->mm after the 'if (p->mm)' check.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 65a5036..96f7701 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -80,13 +80,17 @@
*/
void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
{
+ struct mm_struct *mm;
+
/* convert pages-jiffies to Mbyte-usec */
stats->coremem = jiffies_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB;
stats->virtmem = jiffies_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB;
- if (p->mm) {
+ mm = get_task_mm(p);
+ if (mm) {
/* adjust to KB unit */
- stats->hiwater_rss = p->mm->hiwater_rss * PAGE_SIZE / KB;
- stats->hiwater_vm = p->mm->hiwater_vm * PAGE_SIZE / KB;
+ stats->hiwater_rss = mm->hiwater_rss * PAGE_SIZE / KB;
+ stats->hiwater_vm = mm->hiwater_vm * PAGE_SIZE / KB;
+ mmput(mm);
}
stats->read_char = p->rchar;
stats->write_char = p->wchar;