From 2702b1526c7278c4d65d78de209a465d4de2885e Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 19 Oct 2012 13:56:51 -0700 Subject: [PATCH 1/2] 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 Signed-off-by: Kees Cook Cc: Andi Kleen Cc: PaX Team Cc: Brad Spengler Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sys.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index c5cb5b9..01865c6 100644 --- a/kernel/sys.c +++ b/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 *release, int len) 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; } -- 1.7.12.1 From 31fd84b95eb211d5db460a1dda85e004800a7b52 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 19 Oct 2012 18:45:53 -0700 Subject: [PATCH 2/2] use clamp_t in UNAME26 fix The min/max call needed to have explicit types on some architectures (e.g. mn10300). Use clamp_t instead to avoid the warning: kernel/sys.c: In function 'override_release': kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast [enabled by default] Reported-by: Fengguang Wu Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds --- kernel/sys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sys.c b/kernel/sys.c index 01865c6..e6e0ece 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1284,7 +1284,7 @@ static int override_release(char __user *release, size_t len) rest++; } v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40; - copy = min(sizeof(buf), max_t(size_t, 1, len)); + copy = clamp_t(size_t, len, 1, sizeof(buf)); copy = scnprintf(buf, copy, "2.6.%u%s", v, rest); ret = copy_to_user(release, buf, copy + 1); } -- 1.7.12.1