From 8d5636fbca202f61fdb808fc9e20c0142291d802 Mon Sep 17 00:00:00 2001 From: Jeremy Kerr Date: Thu, 14 Aug 2008 14:59:12 +1000 Subject: [PATCH] powerpc/spufs: reference context while dropping state mutex in scheduler Based on an original patch from Christoph Hellwig . 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 --- arch/powerpc/platforms/cell/spufs/sched.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c index 2deeeba7ecc..4b6b0c3a8c9 100644 --- a/arch/powerpc/platforms/cell/spufs/sched.c +++ b/arch/powerpc/platforms/cell/spufs/sched.c @@ -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); -- 2.20.1