Messages in this thread | | | Date | Mon, 23 Apr 2018 21:13:24 -0600 | From | Tycho Andersen <> | Subject | Re: [PATCH 3/3] dh key: get rid of stack allocated array for zeroes |
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On Mon, Apr 23, 2018 at 07:03:21PM -0600, Tycho Andersen wrote: > We're interested in getting rid of all of the stack allocated arrays in > the kernel: https://lkml.org/lkml/2018/3/7/621 > > This case is interesting, since we really just need an array of bytes that > are zero. The loop already ensures that if the array isn't exactly the > right size that enough zero bytes will be copied in. So, instead of > choosing this value to be the size of the hash, let's just choose it to be > 256, since that is a common size, is not to big, and will not result in too > many extra iterations of the loop. > > v2: split out from other patch, just hardcode array size instead of > dynamically allocating something the right size > > Signed-off-by: Tycho Andersen <tycho@tycho.ws> > CC: David Howells <dhowells@redhat.com> > CC: James Morris <jmorris@namei.org> > CC: "Serge E. Hallyn" <serge@hallyn.com> > CC: Eric Biggers <ebiggers3@gmail.com> > --- > security/keys/dh.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/security/keys/dh.c b/security/keys/dh.c > index 9fecaea6c298..74f8a853872e 100644 > --- a/security/keys/dh.c > +++ b/security/keys/dh.c > @@ -162,8 +162,8 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, > goto err; > > if (zlen && h) { > - u8 tmpbuffer[h]; > - size_t chunk = min_t(size_t, zlen, h); > + u8 tmpbuffer[256];
Whoops, this should be 32, not 256. That shouldn't make any runtime difference, but it'll closer match the allocation patterns from before.
I'll let this sit for a bit and send v3.
Tycho
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