lkml.org 
[lkml]   [2018]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.4 026/193] staging: android: ashmem: Fix a race condition in pin ioctls
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@decadent.org.uk>

commit ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 upstream.

ashmem_pin_unpin() reads asma->file and asma->size before taking the
ashmem_mutex, so it can race with other operations that modify them.

Build-tested only.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/android/ashmem.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -704,30 +704,32 @@ static int ashmem_pin_unpin(struct ashme
size_t pgstart, pgend;
int ret = -EINVAL;

+ mutex_lock(&ashmem_mutex);
+
if (unlikely(!asma->file))
- return -EINVAL;
+ goto out_unlock;

- if (unlikely(copy_from_user(&pin, p, sizeof(pin))))
- return -EFAULT;
+ if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) {
+ ret = -EFAULT;
+ goto out_unlock;
+ }

/* per custom, you can pass zero for len to mean "everything onward" */
if (!pin.len)
pin.len = PAGE_ALIGN(asma->size) - pin.offset;

if (unlikely((pin.offset | pin.len) & ~PAGE_MASK))
- return -EINVAL;
+ goto out_unlock;

if (unlikely(((__u32)-1) - pin.offset < pin.len))
- return -EINVAL;
+ goto out_unlock;

if (unlikely(PAGE_ALIGN(asma->size) < pin.offset + pin.len))
- return -EINVAL;
+ goto out_unlock;

pgstart = pin.offset / PAGE_SIZE;
pgend = pgstart + (pin.len / PAGE_SIZE) - 1;

- mutex_lock(&ashmem_mutex);
-
switch (cmd) {
case ASHMEM_PIN:
ret = ashmem_pin(asma, pgstart, pgend);
@@ -740,6 +742,7 @@ static int ashmem_pin_unpin(struct ashme
break;
}

+out_unlock:
mutex_unlock(&ashmem_mutex);

return ret;

\
 
 \ /
  Last update: 2018-02-23 21:41    [W:0.425 / U:0.180 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site