From: Lasse Collin <lasse.collin@tukaani.org> To: Kees Cook <keescook@chromium.org> Cc: Ingo Molnar <mingo@kernel.org>, Yinghai Lu <yinghai@kernel.org>, Baoquan He <bhe@redhat.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Matt Redfearn <matt.redfearn@imgtec.com>, x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Vivek Goyal <vgoyal@redhat.com>, Andy Lutomirski <luto@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Dave Young <dyoung@redhat.com>, kernel-hardening@lists.openwall.com, LKML <linux-kernel@vger.kernel.org> Subject: Re: [PATCH v5 13/21] x86, boot: Report overlap failures in memcpy Date: Fri, 15 Apr 2016 17:42:31 +0300 [thread overview] Message-ID: <20160415174231.7425bc7a@tukaani.org> (raw) In-Reply-To: <1460672954-32567-14-git-send-email-keescook@chromium.org> On 2016-04-14 Kees Cook wrote: > From: Yinghai Lu <yinghai@kernel.org> > > parse_elf is using a local memcpy to move sections to their final > running position. However, this memcpy only supports non-overlapping > arguments (or dest < src). The same copy of memcpy is used by the decompressors too. > To avoid future hard-to-debug surprises, this adds checking in memcpy > to detect the unhandled condition (which should not be happening > currently). It's already a minor surprise that memcpy is expected to work for overlapping buffers at all. It could be good to have a comment about it because "scroll" and parse_elf seem to rely on it. On the other hand, the new code and error message take quite a few bytes of space, so a complete memmove can be smaller: void *memmove(void *dest, const void *src, size_t n) { unsigned char *d = dest; const unsigned char *s = src; if (d <= s || d - s >= n) return __memcpy(dest, src, n); while (n-- > 0) d[n] = s[n]; return dest; } Note that memmove is needed by lib/decompress_unxz.c. It contains its own small version inside a "#ifndef memmove" block. That #ifndef should be taken into account when adding a memmove symbol. Changing decompress_unxz.c is fine but then one needs to think about other archs too. -- Lasse Collin | IRC: Larhzu @ IRCnet & Freenode
WARNING: multiple messages have this Message-ID (diff)
From: Lasse Collin <lasse.collin@tukaani.org> To: Kees Cook <keescook@chromium.org> Cc: Ingo Molnar <mingo@kernel.org>, Yinghai Lu <yinghai@kernel.org>, Baoquan He <bhe@redhat.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Matt Redfearn <matt.redfearn@imgtec.com>, x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Vivek Goyal <vgoyal@redhat.com>, Andy Lutomirski <luto@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Dave Young <dyoung@redhat.com>, kernel-hardening@lists.openwall.com, LKML <linux-kernel@vger.kernel.org> Subject: [kernel-hardening] Re: [PATCH v5 13/21] x86, boot: Report overlap failures in memcpy Date: Fri, 15 Apr 2016 17:42:31 +0300 [thread overview] Message-ID: <20160415174231.7425bc7a@tukaani.org> (raw) In-Reply-To: <1460672954-32567-14-git-send-email-keescook@chromium.org> On 2016-04-14 Kees Cook wrote: > From: Yinghai Lu <yinghai@kernel.org> > > parse_elf is using a local memcpy to move sections to their final > running position. However, this memcpy only supports non-overlapping > arguments (or dest < src). The same copy of memcpy is used by the decompressors too. > To avoid future hard-to-debug surprises, this adds checking in memcpy > to detect the unhandled condition (which should not be happening > currently). It's already a minor surprise that memcpy is expected to work for overlapping buffers at all. It could be good to have a comment about it because "scroll" and parse_elf seem to rely on it. On the other hand, the new code and error message take quite a few bytes of space, so a complete memmove can be smaller: void *memmove(void *dest, const void *src, size_t n) { unsigned char *d = dest; const unsigned char *s = src; if (d <= s || d - s >= n) return __memcpy(dest, src, n); while (n-- > 0) d[n] = s[n]; return dest; } Note that memmove is needed by lib/decompress_unxz.c. It contains its own small version inside a "#ifndef memmove" block. That #ifndef should be taken into account when adding a memmove symbol. Changing decompress_unxz.c is fine but then one needs to think about other archs too. -- Lasse Collin | IRC: Larhzu @ IRCnet & Freenode
next prev parent reply other threads:[~2016-04-15 14:50 UTC|newest] Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-04-14 22:28 [PATCH v5 00/21] x86, boot: KASLR cleanup and 64-bit improvements Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-14 22:28 ` [PATCH v5 01/21] x86, KASLR: Remove unneeded boot_params argument Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-15 7:29 ` Ingo Molnar 2016-04-15 7:29 ` [kernel-hardening] " Ingo Molnar 2016-04-15 18:55 ` Kees Cook 2016-04-15 18:55 ` [kernel-hardening] " Kees Cook 2016-04-14 22:28 ` [PATCH v5 02/21] x86, KASLR: Handle kernel relocation above 2G Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-15 7:47 ` Ingo Molnar 2016-04-15 7:47 ` [kernel-hardening] " Ingo Molnar 2016-04-15 19:01 ` Kees Cook 2016-04-15 19:01 ` [kernel-hardening] " Kees Cook 2016-04-14 22:28 ` [PATCH v5 03/21] x86, KASLR: Drop CONFIG_RANDOMIZE_BASE_MAX_OFFSET Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-15 8:07 ` Ingo Molnar 2016-04-15 8:07 ` [kernel-hardening] " Ingo Molnar 2016-04-15 19:12 ` Kees Cook 2016-04-15 19:12 ` [kernel-hardening] " Kees Cook 2016-04-16 8:42 ` Ingo Molnar 2016-04-16 8:42 ` [kernel-hardening] " Ingo Molnar 2016-04-14 22:28 ` [PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-15 8:09 ` Ingo Molnar 2016-04-15 8:09 ` [kernel-hardening] " Ingo Molnar 2016-04-18 16:50 ` Kees Cook 2016-04-18 16:50 ` [kernel-hardening] " Kees Cook 2016-04-15 9:05 ` Ingo Molnar 2016-04-15 9:05 ` [kernel-hardening] " Ingo Molnar 2016-04-14 22:28 ` [PATCH v5 05/21] x86, boot: Calculate decompression size during boot not build Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-15 8:12 ` Ingo Molnar 2016-04-15 8:12 ` [kernel-hardening] " Ingo Molnar 2016-04-15 19:14 ` Kees Cook 2016-04-15 19:14 ` [kernel-hardening] " Kees Cook 2016-04-14 22:28 ` [PATCH v5 06/21] x86, KASLR: Update description for decompressor worst case size Kees Cook 2016-04-14 22:28 ` [kernel-hardening] " Kees Cook 2016-04-15 16:17 ` Lasse Collin 2016-04-15 16:17 ` [kernel-hardening] " Lasse Collin 2016-04-14 22:29 ` [PATCH v5 07/21] x86, boot: Fix run_size calculation Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-15 8:31 ` Ingo Molnar 2016-04-15 8:31 ` [kernel-hardening] " Ingo Molnar 2016-04-15 19:26 ` Kees Cook 2016-04-15 19:26 ` [kernel-hardening] " Kees Cook 2016-04-16 9:00 ` Ingo Molnar 2016-04-16 9:00 ` [kernel-hardening] " Ingo Molnar 2016-04-14 22:29 ` [PATCH v5 08/21] x86, KASLR: Clean up unused code from old run_size Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 09/21] x86, KASLR: Correctly bounds-check relocations Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 10/21] x86, KASLR: Consolidate mem_avoid entries Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 11/21] x86, boot: Split out kernel_ident_mapping_init Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 12/21] x86, 64bit: Set ident_mapping for KASLR Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 13/21] x86, boot: Report overlap failures in memcpy Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-15 14:42 ` Lasse Collin [this message] 2016-04-15 14:42 ` [kernel-hardening] " Lasse Collin 2016-04-15 19:28 ` Kees Cook 2016-04-15 19:28 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 14/21] x86, KASLR: Add slot_area to manage random slots Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 15/21] x86, KASLR: Add slot_area support functions Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 16/21] x86, KASLR: Add virtual address choosing function Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 17/21] x86, KASLR: Clarify purpose of each get_random_long Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 18/21] x86, KASLR: Randomize virtual address separately Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 19/21] x86, KASLR: Add physical address randomization >4G Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 20/21] x86, KASLR: Remove unused slot tracking code Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook 2016-04-14 22:29 ` [PATCH v5 21/21] x86, KASLR: Allow randomization below load address Kees Cook 2016-04-14 22:29 ` [kernel-hardening] " Kees Cook
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