Hi, On Fri, Oct 19, 2012 at 1:56 PM, <[email protected]> wrote: > From: Kees Cook <[email protected]> > Subject: kernel/sys.c: fix stack memory content leak via UNAME26 > > Calling uname() with the UNAME26 personality set allows a leak of kernel > stack contents. This fixes it by defensively calculating the length of > copy_to_user() call, making the len argument unsigned, and initializing > the stack buffer to zero (now technically unneeded, but hey, overkill). > > CVE-2012-0957 > > Reported-by: PaX Team <[email protected]> > Signed-off-by: Kees Cook <[email protected]> > Cc: Andi Kleen <[email protected]> > Cc: PaX Team <[email protected]> > Cc: Brad Spengler <[email protected]> > Cc: <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > --- > > kernel/sys.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff -puN kernel/sys.c~kernel-sysc-fix-stack-memory-content-leak-via-uname26 > kernel/sys.c > --- a/kernel/sys.c~kernel-sysc-fix-stack-memory-content-leak-via-uname26 > +++ a/kernel/sys.c > @@ -1265,15 +1265,16 @@ DECLARE_RWSEM(uts_sem); > * Work around broken programs that cannot handle "Linux 3.0". > * Instead we map 3.x to 2.6.40+x, so e.g. 3.0 would be 2.6.40 > */ > -static int override_release(char __user *release, int len) > +static int override_release(char __user *release, size_t len) > { > int ret = 0; > - char buf[65]; > > if (current->personality & UNAME26) { > - char *rest = UTS_RELEASE; > + const char *rest = UTS_RELEASE; > + char buf[65] = { 0 }; > int ndots = 0; > unsigned v; > + size_t copy; > > while (*rest) { > if (*rest == '.' && ++ndots >= 3) > @@ -1283,8 +1284,9 @@ static int override_release(char __user > rest++; > } > v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40; > - snprintf(buf, len, "2.6.%u%s", v, rest); > - ret = copy_to_user(release, buf, len); > + copy = min(sizeof(buf), max_t(size_t, 1, len)); > + copy = scnprintf(buf, copy, "2.6.%u%s", v, rest); > + ret = copy_to_user(release, buf, copy + 1); > } > return ret; > } > _
Please use this improved patch, the one above had an issue that Fengguang Wu found (needed to swap min/max with clamp): https://lkml.org/lkml/2012/10/12/358 Thanks, -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
