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powerpc/spufs: reference context while dropping state mutex in scheduler

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Based on an original patch from Christoph Hellwig <hch@lst.de>.

Currently, there is a possible reference-after-free in the spusched
code - contexts may be freed after we have released their state_mutex
in spusched_tick and find_victim.

This change takes a reference to the context before releasing the
mutex, so that the context doesn't get destroyed.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
This commit is contained in:
Jeremy Kerr 2008-08-14 14:59:12 +10:00
parent d9dd421fd6
commit 8d5636fbca
1 changed files with 8 additions and 1 deletions
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9
arch/powerpc/platforms/cell/spufs/sched.c
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@ -641,8 +641,10 @@ static struct spu *find_victim(struct spu_context *ctx)
if (tmp && tmp->prio > ctx->prio &&
!(tmp->flags & SPU_CREATE_NOSCHED) &&
(!victim || tmp->prio > victim->prio))
(!victim || tmp->prio > victim->prio)) {
victim = spu->ctx;
get_spu_context(victim);
}
}
mutex_unlock(&cbe_spu_info[node].list_mutex);
@ -658,6 +660,7 @@ static struct spu *find_victim(struct spu_context *ctx)
* look at another context or give up after X retries.
*/
if (!mutex_trylock(&victim->state_mutex)) {
put_spu_context(victim);
victim = NULL;
goto restart;
}
@ -670,6 +673,7 @@ static struct spu *find_victim(struct spu_context *ctx)
* restart the search.
*/
mutex_unlock(&victim->state_mutex);
put_spu_context(victim);
victim = NULL;
goto restart;
}
@ -687,6 +691,7 @@ static struct spu *find_victim(struct spu_context *ctx)
spu_add_to_rq(victim);
mutex_unlock(&victim->state_mutex);
put_spu_context(victim);
return spu;
}
@ -985,9 +990,11 @@ static int spusched_thread(void *unused)
struct spu_context *ctx = spu->ctx;
if (ctx) {
get_spu_context(ctx);
mutex_unlock(mtx);
spusched_tick(ctx);
mutex_lock(mtx);
put_spu_context(ctx);
}
}
mutex_unlock(mtx);