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| author | Nadav Amit <namit@vmware.com> | 2019-04-25 17:11:31 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-31 06:46:12 -0700 |
| commit | 8715ce033eb37f539e73b1570bf56404b21d46cd (patch) | |
| tree | dd44e1e97c728fb7f979652b3e5244530f068faa /include/linux | |
| parent | 34f3a58f06da9b4fae215c35ae9a79d86b3c8012 (diff) | |
| download | linux-stable-8715ce033eb37f539e73b1570bf56404b21d46cd.tar.gz linux-stable-8715ce033eb37f539e73b1570bf56404b21d46cd.tar.bz2 linux-stable-8715ce033eb37f539e73b1570bf56404b21d46cd.zip | |
x86/modules: Avoid breaking W^X while loading modules
[ Upstream commit f2c65fb3221adc6b73b0549fc7ba892022db9797 ]
When modules and BPF filters are loaded, there is a time window in
which some memory is both writable and executable. An attacker that has
already found another vulnerability (e.g., a dangling pointer) might be
able to exploit this behavior to overwrite kernel code. Prevent having
writable executable PTEs in this stage.
In addition, avoiding having W+X mappings can also slightly simplify the
patching of modules code on initialization (e.g., by alternatives and
static-key), as would be done in the next patch. This was actually the
main motivation for this patch.
To avoid having W+X mappings, set them initially as RW (NX) and after
they are set as RO set them as X as well. Setting them as executable is
done as a separate step to avoid one core in which the old PTE is cached
(hence writable), and another which sees the updated PTE (executable),
which would break the W^X protection.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <akpm@linux-foundation.org>
Cc: <ard.biesheuvel@linaro.org>
Cc: <deneen.t.dock@intel.com>
Cc: <kernel-hardening@lists.openwall.com>
Cc: <kristen@linux.intel.com>
Cc: <linux_dti@icloud.com>
Cc: <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Link: https://lkml.kernel.org/r/20190426001143.4983-12-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/filter.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index 6ecef32fd8bc..d52a7484aeb2 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -684,6 +684,7 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp) static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) { set_memory_ro((unsigned long)hdr, hdr->pages); + set_memory_x((unsigned long)hdr, hdr->pages); } static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr) |