On Wed, 10 Nov 2010 23:38:02 +0300 Vasiliy Kulikov <segooon@xxxxxxxxx> wrote: > On some architectures __kernel_suseconds_t is int. On sparc and parisc. On all other architectures this patch is a waste of cycles. > On these archs > struct timeval has padding bytes at the end. This struct is copied to > userspace with these padding bytes uninitialized. This leads to leaking > of contents of kernel stack memory. > > This bug was added with v2.6.27-rc5-286-gb773ad4. > > Signed-off-by: Vasiliy Kulikov <segooon@xxxxxxxxx> > --- > Compile tested. > > fs/select.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/fs/select.c b/fs/select.c > index b7b10aa..32cf018 100644 > --- a/fs/select.c > +++ b/fs/select.c > @@ -306,6 +306,7 @@ static int poll_select_copy_remaining(struct timespec *end_time, void __user *p, > rts.tv_sec = rts.tv_nsec = 0; > > if (timeval) { > + memset(&rtv, 0, sizeof(rtv)); > rtv.tv_sec = rts.tv_sec; > rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; How about this? --- a/fs/select.c~fs-select-fix-information-leak-to-userspace-fix +++ a/fs/select.c @@ -306,7 +306,8 @@ static int poll_select_copy_remaining(st rts.tv_sec = rts.tv_nsec = 0; if (timeval) { - memset(&rtv, 0, sizeof(rtv)); + if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) + memset(&rtv, 0, sizeof(rtv)); rtv.tv_sec = rts.tv_sec; rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; _ The `if' gets eliminated at compile time. With this approach we add four bytes of text to the sparc64 build and zero bytes of text to the x86_64 build. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html