From ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Sun, 4 Feb 2018 02:06:27 +0000 Subject: [PATCH] staging: android: ashmem: Fix a race condition in pin ioctls 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. Cc: stable@vger.kernel.org Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ashmem.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index bbdc53b686dd..6dbba5aff191 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -702,30 +702,32 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, size_t pgstart, pgend; int ret = -EINVAL; - if (unlikely(!asma->file)) - return -EINVAL; + mutex_lock(&ashmem_mutex); - if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) - return -EFAULT; + if (unlikely(!asma->file)) + goto out_unlock; + + 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); @@ -738,6 +740,7 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, break; } +out_unlock: mutex_unlock(&ashmem_mutex); return ret;