Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] crypto/caam: Avoid GCC constprop bug warning | Date | Sat, 29 Oct 2022 11:40:55 +0000 |
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From: Kees Cook > Sent: 28 October 2022 22:06 > > GCC 12 appears to perform constant propagation incompletely(?) and can > no longer notice that "len" is always 0 when "data" is NULL. Expand the > check to avoid warnings about memcpy() having a NULL argument: ... > > diff --git a/drivers/crypto/caam/desc_constr.h b/drivers/crypto/caam/desc_constr.h > index 62ce6421bb3f..ddbba8b00ab7 100644 > --- a/drivers/crypto/caam/desc_constr.h > +++ b/drivers/crypto/caam/desc_constr.h > @@ -163,7 +163,7 @@ static inline void append_data(u32 * const desc, const void *data, int len) > { > u32 *offset = desc_end(desc); > > - if (len) /* avoid sparse warning: memcpy with byte count of 0 */ > + if (data && len) /* avoid sparse warning: memcpy with byte count of 0 */ > memcpy(offset, data, len);
I'd guess non-constant zero lengths are unlikely? So how about: /* Avoid calling memcpy() when there is never a buffer */ if (!__builtin_constant(len) || len) memcpy(offset, data, len);
Then the test should never actually end up in the object code.
David
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