2015-01-05 23:27:51

by Daniel Borkmann

Subject: [PATCH] lib: memzero_explicit: add comment for its usage

Lets improve the comment to add a note on when to use memzero_explicit()
for those not digging through the git logs. We don't want people to
pollute places with memzero_explicit() where it's not really necessary.

Reference: https://lkml.org/lkml/2015/1/4/190
Suggested-by: Herbert Xu <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
---
[ Sending to -crypto as it's most relevant here and suggested by
Herbert anyway. ]

lib/string.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/lib/string.c b/lib/string.c
index 1006330..d984ec4 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -604,6 +604,11 @@ EXPORT_SYMBOL(memset);
* @s: Pointer to the start of the area.
* @count: The size of the area.
*
+ * Note: usually using memset() is just fine (!), but in cases
+ * where clearing out _local_ data at the end of a scope is
+ * necessary, memzero_explicit() should be used instead in
+ * order to prevent the compiler from optimising away zeroing.
+ *
* memzero_explicit() doesn't need an arch-specific version as
* it just invokes the one of memset() implicitly.
*/
--
1.7.11.7

2015-01-08 10:49:05

by Herbert Xu

Subject: Re: [PATCH] lib: memzero_explicit: add comment for its usage

On Tue, Jan 06, 2015 at 12:27:45AM +0100, Daniel Borkmann wrote:
> Lets improve the comment to add a note on when to use memzero_explicit()
> for those not digging through the git logs. We don't want people to
> pollute places with memzero_explicit() where it's not really necessary.
>
> Reference: https://lkml.org/lkml/2015/1/4/190
> Suggested-by: Herbert Xu <[email protected]>
> Signed-off-by: Daniel Borkmann <[email protected]>

Applied.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt