linux-kernel - Re: [PATCH] crypto: scatterwalk: propagate errors from failed call to skcipher_walk

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Message-ID: <20251114192810.GA1687@quark>
Date: Fri, 14 Nov 2025 11:28:10 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: Colin Ian King <coking@...dia.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>,
	"David S . Miller" <davem@...emloft.net>,
	linux-crypto@...r.kernel.org, kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: scatterwalk: propagate errors from failed call
 to skcipher_walk_first

On Fri, Nov 14, 2025 at 12:26:19PM +0000, Colin Ian King wrote:
> There are cases where skcipher_walk_first can fail and errors such as
> -ENOMEM or -EDEADLK are being ignored in memcpy_sglist. Add error checks
> and propagate the error down to callers.
> 
> This fixes silent data loss from callers to memcpy_sglist (since walk is
> zero'd) or potential encryption on the wrong data.
> 
> Signed-off-by: Colin Ian King <coking@...dia.com>

There's no need for copying between two scatterlists to be able to fail.
memcpy_sglist() should just be implemented from first principles instead
of misusing the skcipher_walk stuff.  I actually suggested this already
(https://lore.kernel.org/linux-crypto/20250427010834.GB68006@quark/) but
unfortunately it was disregarded.

- Eric