From: David Miller <davem@davemloft.net>
To: geert@linux-m68k.org
Cc: hannes@stressinduktion.org, mkubecek@suse.cz,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-m68k@vger.kernel.org
Subject: Re: [PATCH] net: dst: Force 4-byte alignment of dst_metrics
Date: Fri, 20 Dec 2019 21:54:23 -0800 (PST) [thread overview]
Message-ID: <20191220.215423.1490110825809704417.davem@davemloft.net> (raw)
In-Reply-To: <20191220133140.5684-1-geert@linux-m68k.org>
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Fri, 20 Dec 2019 14:31:40 +0100
> When storing a pointer to a dst_metrics structure in dst_entry._metrics,
> two flags are added in the least significant bits of the pointer value.
> Hence this assumes all pointers to dst_metrics structures have at least
> 4-byte alignment.
>
> However, on m68k, the minimum alignment of 32-bit values is 2 bytes, not
> 4 bytes. Hence in some kernel builds, dst_default_metrics may be only
> 2-byte aligned, leading to obscure boot warnings like:
>
> WARNING: CPU: 0 PID: 7 at lib/refcount.c:28 refcount_warn_saturate+0x44/0x9a
> refcount_t: underflow; use-after-free.
> Modules linked in:
> CPU: 0 PID: 7 Comm: ksoftirqd/0 Tainted: G W 5.5.0-rc2-atari-01448-g114a1a1038af891d-dirty #261
> Stack from 10835e6c:
> 10835e6c 0038134f 00023fa6 00394b0f 0000001c 00000009 00321560 00023fea
> 00394b0f 0000001c 001a70f8 00000009 00000000 10835eb4 00000001 00000000
> 04208040 0000000a 00394b4a 10835ed4 00043aa8 001a70f8 00394b0f 0000001c
> 00000009 00394b4a 0026aba8 003215a4 00000003 00000000 0026d5a8 00000001
> 003215a4 003a4361 003238d6 000001f0 00000000 003215a4 10aa3b00 00025e84
> 003ddb00 10834000 002416a8 10aa3b00 00000000 00000080 000aa038 0004854a
> Call Trace: [<00023fa6>] __warn+0xb2/0xb4
> [<00023fea>] warn_slowpath_fmt+0x42/0x64
> [<001a70f8>] refcount_warn_saturate+0x44/0x9a
> [<00043aa8>] printk+0x0/0x18
> [<001a70f8>] refcount_warn_saturate+0x44/0x9a
> [<0026aba8>] refcount_sub_and_test.constprop.73+0x38/0x3e
> [<0026d5a8>] ipv4_dst_destroy+0x5e/0x7e
> [<00025e84>] __local_bh_enable_ip+0x0/0x8e
> [<002416a8>] dst_destroy+0x40/0xae
>
> Fix this by forcing 4-byte alignment of all dst_metrics structures.
>
> Fixes: e5fd387ad5b30ca3 ("ipv6: do not overwrite inetpeer metrics prematurely")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Applied.
prev parent reply other threads:[~2019-12-21 5:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 13:31 [PATCH] net: dst: Force 4-byte alignment of dst_metrics Geert Uytterhoeven
2019-12-21 5:54 ` David Miller [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191220.215423.1490110825809704417.davem@davemloft.net \
--to=davem@davemloft.net \
--cc=geert@linux-m68k.org \
--cc=hannes@stressinduktion.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-m68k@vger.kernel.org \
--cc=mkubecek@suse.cz \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox