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* gnu/packages/elf.scm (elfutils): Fix cross-compilation [arguments]: When cross-compilation, apply patch. <#:phases>: Use G-expressions. * gnu/packages/patches/elfutils-libdwfl-string-overflow.patch: New file. * gnu/local.mk (dist_patch_DATA): Register it. Change-Id: Ia1ab9c09124a140608bda34bf62f0ae80eb44f9b
116 lines
4.6 KiB
Diff
116 lines
4.6 KiB
Diff
from https://sourceware.org/cgit/elfutils/patch/?id=0873ae782d14e672e8344775e76b7fca0a8b41bf
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Adjust the changelog so it can be applied on elfutils 0.187.
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From 0873ae782d14e672e8344775e76b7fca0a8b41bf Mon Sep 17 00:00:00 2001
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From: Mark Wielaard <mark@klomp.org>
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Date: Thu, 28 Jul 2022 15:31:12 +0200
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Subject: libdwfl: Rewrite reading of ar_size in elf_begin_rand
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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With GCC 12.1.1, glibc 2.35, -fsanitize=undefined and
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-D_FORTIFY_SOURCE=3 we get the following error message:
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In file included from /usr/include/ar.h:22,
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from ../libelf/libelfP.h:33,
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from core-file.c:31:
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In function ‘pread’,
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inlined from ‘pread_retry’ at ../lib/system.h:188:21,
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inlined from ‘elf_begin_rand’ at core-file.c:86:16,
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inlined from ‘core_file_read_eagerly’ at core-file.c:205:15:
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/usr/include/bits/unistd.h:74:10: error: ‘__pread_alias’ writing 58 or more bytes into a region of size 10 overflows the destination [-Werror=stringop-overflow=]
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74 | return __glibc_fortify (pread, __nbytes, sizeof (char),
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| ^~~~~~~~~~~~~~~
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/usr/include/ar.h: In function ‘core_file_read_eagerly’:
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/usr/include/ar.h:41:10: note: destination object ‘ar_size’ of size 10
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41 | char ar_size[10]; /* File size, in ASCII decimal. */
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| ^~~~~~~
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/usr/include/bits/unistd.h:50:16: note: in a call to function ‘__pread_alias’ declared with attribute ‘access (write_only, 2, 3)’
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50 | extern ssize_t __REDIRECT (__pread_alias,
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| ^~~~~~~~~~
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cc1: all warnings being treated as errors
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The warning disappears when dropping either -fsanitize=undefined
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or when using -D_FORTIFY_SOURCE=2. It looks like a false positive.
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But I haven't figured out how/why it happens.
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The code is a little tricky to proof correct though. The ar_size
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field is a not-zero terminated string ASCII decimal, right-padded
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with spaces. Which is then converted with strtoll. Relying on the
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fact that the struct ar_hdr is zero initialized, so there will be
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a zero byte after the ar_size field.
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Rewrite the code to just use a zero byte terminated char array.
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Which is much easier to reason about. As a bonus the error disappears.
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Signed-off-by: Mark Wielaard <mark@klomp.org>
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---
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libdwfl/ChangeLog | 5 +++++
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libdwfl/core-file.c | 26 ++++++++++++++++----------
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2 files changed, 21 insertions(+), 10 deletions(-)
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diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
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index 75c53948d..acdaa0138 100644
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--- a/libdwfl/ChangeLog
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+++ b/libdwfl/ChangeLog
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@@ -1,0 +1,5 @@
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+2022-07-28 Mark Wielaard <mark@klomp.org>
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+
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+ * core-file.c (elf_begin_rand): Replace struct ar_hdr h with
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+ a char ar_size[AR_SIZE_CHARS + 1] array to read size.
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+
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2022-04-22 Mark Wielaard <mark@klomp.org>
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* debuginfod-client.c (init_control): New static pthread_once_t.
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diff --git a/libdwfl/core-file.c b/libdwfl/core-file.c
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index cefc3db0f..4418ef338 100644
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--- a/libdwfl/core-file.c
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+++ b/libdwfl/core-file.c
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@@ -75,26 +75,32 @@ elf_begin_rand (Elf *parent, off_t offset, off_t size, off_t *next)
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from the archive header to override SIZE. */
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if (parent->kind == ELF_K_AR)
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{
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- struct ar_hdr h = { .ar_size = "" };
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-
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- if (unlikely (parent->maximum_size - offset < sizeof h))
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+ /* File size, in ASCII decimal, right-padded with ASCII spaces.
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+ Max 10 characters. Not zero terminated. So make this ar_size
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+ array one larger and explicitly zero terminate it. As needed
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+ for strtoll. */
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+ #define AR_SIZE_CHARS 10
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+ char ar_size[AR_SIZE_CHARS + 1];
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+ ar_size[AR_SIZE_CHARS] = '\0';
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+
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+ if (unlikely (parent->maximum_size - offset < sizeof (struct ar_hdr)))
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return fail (ELF_E_RANGE);
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if (parent->map_address != NULL)
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- memcpy (h.ar_size, parent->map_address + parent->start_offset + offset,
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- sizeof h.ar_size);
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+ memcpy (ar_size, parent->map_address + parent->start_offset + offset,
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+ AR_SIZE_CHARS);
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else if (unlikely (pread_retry (parent->fildes,
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- h.ar_size, sizeof (h.ar_size),
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+ ar_size, AR_SIZE_CHARS,
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parent->start_offset + offset
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+ offsetof (struct ar_hdr, ar_size))
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- != sizeof (h.ar_size)))
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+ != AR_SIZE_CHARS))
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return fail (ELF_E_READ_ERROR);
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- offset += sizeof h;
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+ offset += sizeof (struct ar_hdr);
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char *endp;
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- size = strtoll (h.ar_size, &endp, 10);
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- if (unlikely (endp == h.ar_size)
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+ size = strtoll (ar_size, &endp, 10);
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+ if (unlikely (endp == ar_size)
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|| unlikely ((off_t) parent->maximum_size - offset < size))
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return fail (ELF_E_INVALID_ARCHIVE);
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}
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--
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cgit
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