The commit is pushed to "branch-rh7-3.10.0-693.1.1.vz7.37.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.1.1.vz7.37.4
------>
commit 3e990c7b0ba7321ee04ddc7dbece6edc3afea0b0
Author: David Rientjes <rient...@google.com>
Date: Fri Sep 15 17:27:30 2017 +0300
mm, mempolicy: task->mempolicy must be NULL before dropping final reference
KASAN allocates memory from the page allocator as part of
kmem_cache_free(), and that can reference current->mempolicy through any
number of allocation functions. It needs to be NULL'd out before the
final reference is dropped to prevent a use-after-free bug:
BUG: KASAN: use-after-free in alloc_pages_current+0x363/0x370 at addr
ffff88010b48102c
CPU: 0 PID: 15425 Comm: trinity-c2 Not tainted 4.8.0-rc2+ #140
...
Call Trace:
dump_stack
kasan_object_err
kasan_report_error
__asan_report_load2_noabort
alloc_pages_current <-- use after free
depot_save_stack
save_stack
kasan_slab_free
kmem_cache_free
__mpol_put <-- free
do_exit
This patch sets current->mempolicy to NULL before dropping the final
reference.
Link:
http://lkml.kernel.org/r/alpine.deb.2.10.1608301442180.63...@chino.kir.corp.google.com
Fixes: cd11016e5f52 ("mm, kasan: stackdepot implementation. Enable
stackdepot for SLAB")
Signed-off-by: David Rientjes <rient...@google.com>
Reported-by: Vegard Nossum <vegard.nos...@oracle.com>
Acked-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
Cc: Alexander Potapenko <gli...@google.com>
Cc: Dmitry Vyukov <dvyu...@google.com>
Cc: <sta...@vger.kernel.org> [4.6+]
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
https://jira.sw.ru/browse/PSBM-69081
(cherry picked from commit c11600e4fed67ae4cd6a8096936afd445410e8ed)
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
---
include/linux/mempolicy.h | 4 ++++
kernel/exit.c | 7 +------
mm/mempolicy.c | 17 +++++++++++++++++
3 files changed, 22 insertions(+), 6 deletions(-)
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 7f26526..7e47465 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -196,6 +196,7 @@ static inline int vma_migratable(struct vm_area_struct *vma)
}
extern int mpol_misplaced(struct page *, struct vm_area_struct *, unsigned
long);
+extern void mpol_put_task_policy(struct task_struct *);
#else
@@ -320,5 +321,8 @@ static inline int mpol_misplaced(struct page *page, struct
vm_area_struct *vma,
return -1; /* no node preference */
}
+static inline void mpol_put_task_policy(struct task_struct *task)
+{
+}
#endif /* CONFIG_NUMA */
#endif
diff --git a/kernel/exit.c b/kernel/exit.c
index 668cacf..32b7ba2 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -866,12 +866,7 @@ void do_exit(long code)
ptrace_put_breakpoints(tsk);
exit_notify(tsk, group_dead);
-#ifdef CONFIG_NUMA
- task_lock(tsk);
- mpol_put(tsk->mempolicy);
- tsk->mempolicy = NULL;
- task_unlock(tsk);
-#endif
+ mpol_put_task_policy(tsk);
#ifdef CONFIG_FUTEX
if (unlikely(current->pi_state_cache))
kfree(current->pi_state_cache);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9b78006..a2e2422 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2377,6 +2377,23 @@ int mpol_misplaced(struct page *page, struct
vm_area_struct *vma, unsigned long
return ret;
}
+/*
+ * Drop the (possibly final) reference to task->mempolicy. It needs to be
+ * dropped after task->mempolicy is set to NULL so that any allocation done as
+ * part of its kmem_cache_free(), such as by KASAN, doesn't reference a freed
+ * policy.
+ */
+void mpol_put_task_policy(struct task_struct *task)
+{
+ struct mempolicy *pol;
+
+ task_lock(task);
+ pol = task->mempolicy;
+ task->mempolicy = NULL;
+ task_unlock(task);
+ mpol_put(pol);
+}
+
static void sp_delete(struct shared_policy *sp, struct sp_node *n)
{
pr_debug("deleting %lx-l%lx\n", n->start, n->end);
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