Herbert Xu writes:
> On Mon, Aug 31, 2009 at 11:11:42AM -0500, Brad Bosch wrote:
> >
> > OK. I was looking for something subtle because the crash takes a long
> > time to happen. But do you agree that the race I described above also
> > a real bug?
>
> No I don't think it is. CHAINV_STATE_INUSE guarantees that only
> one entity can use ctx->err at any time.
I don't see how you are protecting ctx->err with the INUSE flag. For
example:
If two threads enter async_chainiv_givencrypt at the same time, one
thread will call async_chainiv_postpone_request (INUSE will be clear
until set by async_chainiv_postpone_request) and the other thread will
call async_chainiv_givencrypt_tail (INUSE may or may not be set yet).
Now, ctx-err may be used by both async_chainiv_postpone_request to
store the return value from skcipher_enqueue_givcrypt and by
async_chainiv_givencrypt_tail to store the return value from
crypto_ablkcipher_encrypt at the same time. This can cause the
calling function to think async_chainiv_givencrypt has completed it's
work, when in fact, the work was defered.
The patch I proposed earlier (included again below) avoids this and
also makes the error handling simpler and more direct without
requiring ctx->err at all. I still don't understand why ctx->err was
required in the first place.
Did I miss something with regard to the use of ctx->err?
Now, as to the other bug...
>
> Where we subtract the offset the pointer can never be NULL. Please
> try my patch.
OK. I see now that your offset patch should indeed solve that
problem. But why did you choose to fix it in a complex way? My
suggestion just adds a single test while yours adds new parameters, a
new function and an extra function call.
Thanks for your help.
--Brad
Index: chainiv.c
===================================================================
RCS file: /share/cvs/sdg/kernels/kernel.wms/kernel_2_6_27/src/crypto/chainiv.c,v
retrieving revision 1.1.1.1.4.2
diff -u -r1.1.1.1.4.2 chainiv.c
--- chainiv.c 10 Mar 2009 05:16:24 -0000 1.1.1.1.4.2
+++ chainiv.c 27 Aug 2009 19:40:27 -0000
@@ -36,7 +36,6 @@
unsigned long state;
spinlock_t lock;
- int err;
struct crypto_queue queue;
struct work_struct postponed;
@@ -114,10 +113,9 @@
return chainiv_init_common(tfm);
}
-static int async_chainiv_schedule_work(struct async_chainiv_ctx *ctx)
+static void async_chainiv_schedule_work(struct async_chainiv_ctx *ctx)
{
int queued;
- int err = ctx->err;
if (!ctx->queue.qlen) {
smp_mb__before_clear_bit();
@@ -125,14 +123,11 @@
if (!ctx->queue.qlen ||
test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
- goto out;
+ return;
}
queued = schedule_work(&ctx->postponed);
BUG_ON(!queued);
-
-out:
- return err;
}
static int async_chainiv_postpone_request(struct skcipher_givcrypt_request *req)
@@ -148,8 +143,8 @@
if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
return err;
- ctx->err = err;
- return async_chainiv_schedule_work(ctx);
+ async_chainiv_schedule_work(ctx);
+ return err;
}
static int async_chainiv_givencrypt_tail(struct skcipher_givcrypt_request *req)
@@ -158,18 +153,20 @@
struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
unsigned int ivsize = crypto_ablkcipher_ivsize(geniv);
+ int err;
memcpy(req->giv, ctx->iv, ivsize);
memcpy(subreq->info, ctx->iv, ivsize);
- ctx->err = crypto_ablkcipher_encrypt(subreq);
- if (ctx->err)
+ err = crypto_ablkcipher_encrypt(subreq);
+ if (err)
goto out;
memcpy(ctx->iv, subreq->info, ivsize);
out:
- return async_chainiv_schedule_work(ctx);
+ async_chainiv_schedule_work(ctx);
+ return err;
}
static int async_chainiv_givencrypt(struct skcipher_givcrypt_request *req)
@@ -236,7 +233,7 @@
spin_unlock_bh(&ctx->lock);
if (!req) {
- async_chainiv_schedule_work(ctx);
+ async_chainiv_schedule_work(ctx);
return;
}
--
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