From f0ec1aaf54caddd21c259aea8b2ecfbde4ee4fb9 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 29 Oct 2006 22:46:43 -0800 Subject: [PATCH] [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 Cc: Shailabh Nagar Cc: Balbir Singh Cc: Jay Lan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/tsacct.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/tsacct.c b/kernel/tsacct.c index 65a5036a3d95..96f77013d3f0 100644 --- a/kernel/tsacct.c +++ b/kernel/tsacct.c @@ -80,13 +80,17 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk) */ 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; -- 2.20.1