This is a note to let you know that I've just added the patch titled
xfrm: Avoid clang fortify warning in copy_to_user_tmpl()
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xfrm-avoid-clang-fortify-warning-in-copy_to_user_tmpl.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1a807e46aa93ebad1dfbed4f82dc3bf779423a6e Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@xxxxxxxxxx>
Date: Wed, 21 Feb 2024 14:46:21 -0700
Subject: xfrm: Avoid clang fortify warning in copy_to_user_tmpl()
From: Nathan Chancellor <nathan@xxxxxxxxxx>
commit 1a807e46aa93ebad1dfbed4f82dc3bf779423a6e upstream.
After a couple recent changes in LLVM, there is a warning (or error with
CONFIG_WERROR=y or W=e) from the compile time fortify source routines,
specifically the memset() in copy_to_user_tmpl().
In file included from net/xfrm/xfrm_user.c:14:
...
include/linux/fortify-string.h:438:4: error: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning]
438 | __write_overflow_field(p_size_field, size);
| ^
1 error generated.
While ->xfrm_nr has been validated against XFRM_MAX_DEPTH when its value
is first assigned in copy_templates() by calling validate_tmpl() first
(so there should not be any issue in practice), LLVM/clang cannot really
deduce that across the boundaries of these functions. Without that
knowledge, it cannot assume that the loop stops before i is greater than
XFRM_MAX_DEPTH, which would indeed result a stack buffer overflow in the
memset().
To make the bounds of ->xfrm_nr clear to the compiler and add additional
defense in case copy_to_user_tmpl() is ever used in a path where
->xfrm_nr has not been properly validated against XFRM_MAX_DEPTH first,
add an explicit bound check and early return, which clears up the
warning.
Cc: stable@xxxxxxxxxxxxxxx
Link: https://github.com/ClangBuiltLinux/linux/issues/1985
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/xfrm/xfrm_user.c | 3 +++
1 file changed, 3 insertions(+)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1704,6 +1704,9 @@ static int copy_to_user_tmpl(struct xfrm
if (xp->xfrm_nr == 0)
return 0;
+ if (xp->xfrm_nr > XFRM_MAX_DEPTH)
+ return -ENOBUFS;
+
for (i = 0; i < xp->xfrm_nr; i++) {
struct xfrm_user_tmpl *up = &vec[i];
struct xfrm_tmpl *kp = &xp->xfrm_vec[i];
Patches currently in stable-queue which might be from nathan@xxxxxxxxxx are
queue-5.4/kbuild-move-wenum-compare-conditional-enum-conversio.patch
queue-5.4/memtest-use-read-write-_once-in-memory-scanning.patch
queue-5.4/xfrm-avoid-clang-fortify-warning-in-copy_to_user_tmpl.patch
