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Commit 484dd30e authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Greg Kroah-Hartman
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persistent_ram: Fix buffer size clamping during writes 



This is a longstanding bug, almost unnoticeable when calling
persistent_ram_write() for small buffers.

But when called for large data buffers, the write routine behaves
incorrectly, as the size may never update: instead of clamping
the size to the maximum buffer size, buffer_size_add_clamp() returns
an error (which is never checked by the write routine, btw).

To fix this, we now use buffer_size_add() that actually clamps the
size to the max value.

Also remove buffer_size_add_clamp(), it is no longer needed.

Signed-off-by: default avatarAnton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: default avatarColin Cross <ccross@android.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 06f3d3bd

drivers/staging/android/persistent_ram.c

+1 −18
Original line number Diff line number Diff line
@@ -79,23 +79,6 @@ static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a) 
	} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);

}



/* increase the size counter, retuning an error if it hits the max size */

static inline ssize_t buffer_size_add_clamp(struct persistent_ram_zone *prz,

	size_t a)

{

	size_t old;

	size_t new;



	do {

		old = atomic_read(&prz->buffer->size);

		new = old + a;

		if (new > prz->buffer_size)

			return -ENOMEM;

	} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);



	return 0;

}



static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,

	uint8_t *data, size_t len, uint8_t *ecc)

{
@@ -300,7 +283,7 @@ int notrace persistent_ram_write(struct persistent_ram_zone *prz, 
		c = prz->buffer_size;

	}



	buffer_size_add_clamp(prz, c);

	buffer_size_add(prz, c);



	start = buffer_start_add(prz, c);