Commit-ID: 018ef8dcf3de5f62e2cc1a9273cc27e1c6ba8de5 Gitweb: http://git.kernel.org/tip/018ef8dcf3de5f62e2cc1a9273cc27e1c6ba8de5 Author: Kees Cook <keesc...@chromium.org> AuthorDate: Wed, 17 Feb 2016 14:41:17 -0800 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 22 Feb 2016 08:51:39 +0100
x86/vdso: Mark the vDSO code read-only after init The vDSO does not need to be writable after __init, so mark it as __ro_after_init. The result kills the exploit method of writing to the vDSO from kernel space resulting in userspace executing the modified code, as shown here to bypass SMEP restrictions: http://itszn.com/blog/?p=21 The memory map (with added vDSO address reporting) shows the vDSO moving into read-only memory: Before: [ 0.143067] vDSO @ ffffffff82004000 [ 0.143551] vDSO @ ffffffff82006000 ---[ High Kernel Mapping ]--- 0xffffffff80000000-0xffffffff81000000 16M pmd 0xffffffff81000000-0xffffffff81800000 8M ro PSE GLB x pmd 0xffffffff81800000-0xffffffff819f3000 1996K ro GLB x pte 0xffffffff819f3000-0xffffffff81a00000 52K ro NX pte 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd 0xffffffff81e00000-0xffffffff81e05000 20K ro GLB NX pte 0xffffffff81e05000-0xffffffff82000000 2028K ro NX pte 0xffffffff82000000-0xffffffff8214f000 1340K RW GLB NX pte 0xffffffff8214f000-0xffffffff82281000 1224K RW NX pte 0xffffffff82281000-0xffffffff82400000 1532K RW GLB NX pte 0xffffffff82400000-0xffffffff83200000 14M RW PSE GLB NX pmd 0xffffffff83200000-0xffffffffc0000000 974M pmd After: [ 0.145062] vDSO @ ffffffff81da1000 [ 0.146057] vDSO @ ffffffff81da4000 ---[ High Kernel Mapping ]--- 0xffffffff80000000-0xffffffff81000000 16M pmd 0xffffffff81000000-0xffffffff81800000 8M ro PSE GLB x pmd 0xffffffff81800000-0xffffffff819f3000 1996K ro GLB x pte 0xffffffff819f3000-0xffffffff81a00000 52K ro NX pte 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd 0xffffffff81e00000-0xffffffff81e0b000 44K ro GLB NX pte 0xffffffff81e0b000-0xffffffff82000000 2004K ro NX pte 0xffffffff82000000-0xffffffff8214c000 1328K RW GLB NX pte 0xffffffff8214c000-0xffffffff8227e000 1224K RW NX pte 0xffffffff8227e000-0xffffffff82400000 1544K RW GLB NX pte 0xffffffff82400000-0xffffffff83200000 14M RW PSE GLB NX pmd 0xffffffff83200000-0xffffffffc0000000 974M pmd Based on work by PaX Team and Brad Spengler. Signed-off-by: Kees Cook <keesc...@chromium.org> Acked-by: Andy Lutomirski <l...@kernel.org> Acked-by: H. Peter Anvin <h...@linux.intel.com> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Arnd Bergmann <a...@arndb.de> Cc: Borislav Petkov <b...@alien8.de> Cc: Brad Spengler <spen...@grsecurity.net> Cc: Brian Gerst <brge...@gmail.com> Cc: David Brown <david.br...@linaro.org> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Emese Revfy <re.em...@gmail.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mathias Krause <mini...@googlemail.com> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: PaX Team <pagee...@freemail.hu> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: kernel-harden...@lists.openwall.com Cc: linux-arch <linux-a...@vger.kernel.org> Link: http://lkml.kernel.org/r/1455748879-21872-7-git-send-email-keesc...@chromium.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/entry/vdso/vdso2c.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h index 0224987..3f69326 100644 --- a/arch/x86/entry/vdso/vdso2c.h +++ b/arch/x86/entry/vdso/vdso2c.h @@ -140,7 +140,7 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len, fprintf(outfile, "#include <asm/vdso.h>\n"); fprintf(outfile, "\n"); fprintf(outfile, - "static unsigned char raw_data[%lu] __page_aligned_data = {", + "static unsigned char raw_data[%lu] __ro_after_init __aligned(PAGE_SIZE) = {", mapping_size); for (j = 0; j < stripped_len; j++) { if (j % 10 == 0)
