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Commit de40920f authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Greg Kroah-Hartman
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staging: android: ashmem: Avoid range_alloc() allocation with ashmem_mutex held. 



commit ecd182cbf4e107928077866399100228d2359c60 upstream.

ashmem_pin() is calling range_shrink() without checking whether
range_alloc() succeeded. Also, doing memory allocation with ashmem_mutex
held should be avoided because ashmem_shrink_scan() tries to hold it.

Therefore, move memory allocation for range_alloc() to ashmem_pin_unpin()
and make range_alloc() not to fail.

This patch is mostly meant for backporting purpose for fuzz testing on
stable/distributor kernels, for there is a plan to remove this code in
near future.

Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarJoel Fernandes <joel@joelfernandes.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b8d048b7

drivers/staging/android/ashmem.c

+24 −18
Original line number Diff line number Diff line
@@ -171,19 +171,15 @@ static inline void lru_del(struct ashmem_range *range) 
 * @end:	   The ending page (inclusive)

 *

 * This function is protected by ashmem_mutex.

 *

 * Return: 0 if successful, or -ENOMEM if there is an error

 */

static int range_alloc(struct ashmem_area *asma,

static void range_alloc(struct ashmem_area *asma,

			struct ashmem_range *prev_range, unsigned int purged,

		       size_t start, size_t end)

			size_t start, size_t end,

			struct ashmem_range **new_range)

{

	struct ashmem_range *range;



	range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);

	if (!range)

		return -ENOMEM;

	struct ashmem_range *range = *new_range;



	*new_range = NULL;

	range->asma = asma;

	range->pgstart = start;

	range->pgend = end;
@@ -193,8 +189,6 @@ static int range_alloc(struct ashmem_area *asma, 


	if (range_on_lru(range))

		lru_add(range);



	return 0;

}



/**
@@ -596,7 +590,8 @@ static int get_name(struct ashmem_area *asma, void __user *name) 
 *

 * Caller must hold ashmem_mutex.

 */

static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend)

static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend,

		      struct ashmem_range **new_range)

{

	struct ashmem_range *range, *next;

	int ret = ASHMEM_NOT_PURGED;
@@ -649,7 +644,7 @@ static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend) 
			 * second half and adjust the first chunk's endpoint.

			 */

			range_alloc(asma, range, range->purged,

				    pgend + 1, range->pgend);

				    pgend + 1, range->pgend, new_range);

			range_shrink(range, range->pgstart, pgstart - 1);

			break;

		}
@@ -663,7 +658,8 @@ static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend) 
 *

 * Caller must hold ashmem_mutex.

 */

static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend)

static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend,

			struct ashmem_range **new_range)

{

	struct ashmem_range *range, *next;

	unsigned int purged = ASHMEM_NOT_PURGED;
@@ -689,7 +685,8 @@ static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend) 
		}

	}



	return range_alloc(asma, range, purged, pgstart, pgend);

	range_alloc(asma, range, purged, pgstart, pgend, new_range);

	return 0;

}



/*
@@ -722,10 +719,17 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, 
	struct ashmem_pin pin;

	size_t pgstart, pgend;

	int ret = -EINVAL;

	struct ashmem_range *range = NULL;



	if (copy_from_user(&pin, p, sizeof(pin)))

		return -EFAULT;



	if (cmd == ASHMEM_PIN || cmd == ASHMEM_UNPIN) {

		range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);

		if (!range)

			return -ENOMEM;

	}



	mutex_lock(&ashmem_mutex);

	wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight));
@@ -750,10 +754,10 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, 


	switch (cmd) {

	case ASHMEM_PIN:

		ret = ashmem_pin(asma, pgstart, pgend);

		ret = ashmem_pin(asma, pgstart, pgend, &range);

		break;

	case ASHMEM_UNPIN:

		ret = ashmem_unpin(asma, pgstart, pgend);

		ret = ashmem_unpin(asma, pgstart, pgend, &range);

		break;

	case ASHMEM_GET_PIN_STATUS:

		ret = ashmem_get_pin_status(asma, pgstart, pgend);
@@ -762,6 +766,8 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, 


out_unlock:

	mutex_unlock(&ashmem_mutex);

	if (range)

		kmem_cache_free(ashmem_range_cachep, range);



	return ret;

}