|author||Alexander Popov <email@example.com>||2018-08-17 01:16:58 +0300|
|committer||Kees Cook <firstname.lastname@example.org>||2018-09-04 10:35:47 -0700|
|parent||Linux 4.19-rc2 (diff)|
x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls
The STACKLEAK feature (initially developed by PaX Team) has the following benefits: 1. Reduces the information that can be revealed through kernel stack leak bugs. The idea of erasing the thread stack at the end of syscalls is similar to CONFIG_PAGE_POISONING and memzero_explicit() in kernel crypto, which all comply with FDP_RIP.2 (Full Residual Information Protection) of the Common Criteria standard. 2. Blocks some uninitialized stack variable attacks (e.g. CVE-2017-17712, CVE-2010-2963). That kind of bugs should be killed by improving C compilers in future, which might take a long time. This commit introduces the code filling the used part of the kernel stack with a poison value before returning to userspace. Full STACKLEAK feature also contains the gcc plugin which comes in a separate commit. The STACKLEAK feature is ported from grsecurity/PaX. More information at: https://grsecurity.net/ https://pax.grsecurity.net/ This code is modified from Brad Spengler/PaX Team's code in the last public patch of grsecurity/PaX based on our understanding of the code. Changes or omissions from the original code are ours and don't reflect the original grsecurity/PaX code. Performance impact: Hardware: Intel Core i7-4770, 16 GB RAM Test #1: building the Linux kernel on a single core 0.91% slowdown Test #2: hackbench -s 4096 -l 2000 -g 15 -f 25 -P 4.2% slowdown So the STACKLEAK description in Kconfig includes: "The tradeoff is the performance impact: on a single CPU system kernel compilation sees a 1% slowdown, other systems and workloads may vary and you are advised to test this feature on your expected workload before deploying it". Signed-off-by: Alexander Popov <email@example.com> Acked-by: Thomas Gleixner <firstname.lastname@example.org> Reviewed-by: Dave Hansen <email@example.com> Acked-by: Ingo Molnar <firstname.lastname@example.org> Signed-off-by: Kees Cook <email@example.com>
Diffstat (limited to 'arch/Kconfig')
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 6801123932a5..ee79ff56faab 100644
@@ -419,6 +419,13 @@ config SECCOMP_FILTER
See Documentation/userspace-api/seccomp_filter.rst for details.
+ An architecture should select this if it has the code which
+ fills the used part of the kernel stack with the STACKLEAK_POISON
+ value before returning from system calls.