Bug#472269: libc6: res_query makes assumptions about the alignment of the answer argument
Package: libc6
Followup-For: Bug #472269
Dear Maintainer,
I believe this bug is fixed upstream by the following commit:
commit 05dec22d7be722987ff07aebf9690f6078b3c4e9 (HEAD -> master, origin/master,
origin/HEAD)
Author: John David Anglin <danglin@gcc.gnu.org>
Date: Tue Mar 22 17:35:54 2022 +0000
resolv: Fix unaligned accesses to fields in HEADER struct
The structure HEADER is normally aligned to a word boundary but
sometimes it needs to be accessed when aligned on a byte boundary.
This change defines a new typedef, UHEADER, with alignment 1.
It is used to ensure the fields are accessed with byte loads and
stores when necessary.
V4: Change to res_mkquery.c deleted. Small whitespace fix.
V5: Move UHEADER typedef to resolv/resolv-internal.h. Replace all
HEADER usage with UHEADER in resolv/res_send.c.
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This bug is fixed in debian 2.33 by the patch
any/submitted-resolv-unaligned.diff. It turns out the following
hunk can be removed:
diff --git a/resolv/res_mkquery.c b/resolv/res_mkquery.c
index 5bc5b41531..9b82c82157 100644
--- a/resolv/res_mkquery.c
+++ b/resolv/res_mkquery.c
@@ -193,6 +193,15 @@ context_mkquery_common (struct resolv_context *ctx,
return result;
}
+/* The structure HEADER is normally aligned to a word boundary and its
+ fields are accessed using word loads and stores. We need to access
+ this structure when it is aligned on a byte boundary. This can cause
+ problems on machines with strict alignment. So, we create a new
+ typedef to reduce its alignment to one. This ensures the fields are
+ accessed with byte loads and stores. */
+typedef HEADER __attribute__ ((__aligned__(1))) UHEADER;
+#define HEADER UHEADER
+
/* Form all types of queries. Returns the size of the result or -1 on
error.
Regards,
Dave Anglin
-- System Information:
Debian Release: bookworm/sid
APT prefers buildd-unstable
APT policy: (500, 'buildd-unstable'), (500, 'unstable')
Architecture: hppa (parisc64)
Kernel: Linux 5.16.16+ (SMP w/4 CPU threads)
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages libc6 depends on:
ii libgcc-s4 12-20220319-1
Versions of packages libc6 recommends:
ii libidn2-0 2.3.2-2
Versions of packages libc6 suggests:
ii debconf [debconf-2.0] 1.5.79
ii glibc-doc 2.33-7
ii libc-l10n 2.33-7
ii libnss-nis 3.1-4
ii libnss-nisplus 1.3-4
ii locales 2.33-7
-- debconf information excluded
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