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persistent_ram: Fix buffer size clamping during writes

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commit 484dd30e01 upstream.

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.

Change-Id: Iedde6ab812153ad47aabed3dfe5060356cdeeb55
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Anton Vorontsov 2012-05-11 17:17:17 -07:00 committed by Zhao Wei Liew
parent 6b4fd41bb0
commit 91960cadbd
1 changed files with 1 additions and 18 deletions
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19
drivers/staging/android/persistent_ram.c
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@ -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)
{
@ -304,7 +287,7 @@ 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);