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From 2702b1526c7278c4d65d78de209a465d4de2885e Mon Sep 17 00:00:00 2001
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From: Kees Cook <keescook@chromium.org>
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Date: Fri, 19 Oct 2012 13:56:51 -0700
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Subject: [PATCH 1/2] kernel/sys.c: fix stack memory content leak via UNAME26
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Calling uname() with the UNAME26 personality set allows a leak of kernel
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stack contents. This fixes it by defensively calculating the length of
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copy_to_user() call, making the len argument unsigned, and initializing
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the stack buffer to zero (now technically unneeded, but hey, overkill).
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CVE-2012-0957
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Reported-by: PaX Team <pageexec@freemail.hu>
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Signed-off-by: Kees Cook <keescook@chromium.org>
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Cc: Andi Kleen <ak@linux.intel.com>
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Cc: PaX Team <pageexec@freemail.hu>
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Cc: Brad Spengler <spender@grsecurity.net>
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Cc: <stable@vger.kernel.org>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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kernel/sys.c | 12 +++++++-----
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1 file changed, 7 insertions(+), 5 deletions(-)
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diff --git a/kernel/sys.c b/kernel/sys.c
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index c5cb5b9..01865c6 100644
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--- a/kernel/sys.c
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+++ b/kernel/sys.c
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@@ -1265,15 +1265,16 @@ DECLARE_RWSEM(uts_sem);
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* Work around broken programs that cannot handle "Linux 3.0".
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* Instead we map 3.x to 2.6.40+x, so e.g. 3.0 would be 2.6.40
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*/
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-static int override_release(char __user *release, int len)
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+static int override_release(char __user *release, size_t len)
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{
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int ret = 0;
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- char buf[65];
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if (current->personality & UNAME26) {
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- char *rest = UTS_RELEASE;
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+ const char *rest = UTS_RELEASE;
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+ char buf[65] = { 0 };
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int ndots = 0;
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unsigned v;
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+ size_t copy;
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while (*rest) {
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if (*rest == '.' && ++ndots >= 3)
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@@ -1283,8 +1284,9 @@ static int override_release(char __user *release, int len)
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rest++;
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}
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v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
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- snprintf(buf, len, "2.6.%u%s", v, rest);
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- ret = copy_to_user(release, buf, len);
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+ copy = min(sizeof(buf), max_t(size_t, 1, len));
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+ copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
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+ ret = copy_to_user(release, buf, copy + 1);
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}
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return ret;
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}
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--
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1.7.12.1
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From 31fd84b95eb211d5db460a1dda85e004800a7b52 Mon Sep 17 00:00:00 2001
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From: Kees Cook <keescook@chromium.org>
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Date: Fri, 19 Oct 2012 18:45:53 -0700
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Subject: [PATCH 2/2] use clamp_t in UNAME26 fix
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The min/max call needed to have explicit types on some architectures
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(e.g. mn10300). Use clamp_t instead to avoid the warning:
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kernel/sys.c: In function 'override_release':
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kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast [enabled by default]
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Reported-by: Fengguang Wu <fengguang.wu@intel.com>
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Signed-off-by: Kees Cook <keescook@chromium.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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kernel/sys.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/kernel/sys.c b/kernel/sys.c
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index 01865c6..e6e0ece 100644
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--- a/kernel/sys.c
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+++ b/kernel/sys.c
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@@ -1284,7 +1284,7 @@ static int override_release(char __user *release, size_t len)
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rest++;
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}
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v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
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- copy = min(sizeof(buf), max_t(size_t, 1, len));
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+ copy = clamp_t(size_t, len, 1, sizeof(buf));
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copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
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ret = copy_to_user(release, buf, copy + 1);
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}
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--
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1.7.12.1
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