From: Petr Mladek <pmladek@suse.com>
To: Stephen Boyd <swboyd@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, Joe Perches <joe@perches.com>
Subject: Re: [PATCH v3 4/4] slub: Force on no_hash_pointers when slub_debug is enabled
Date: Thu, 3 Jun 2021 15:15:24 +0200 [thread overview]
Message-ID: <YLjV7JLb2lmegRW9@alley> (raw)
In-Reply-To: <20210601182202.3011020-5-swboyd@chromium.org>
On Tue 2021-06-01 11:22:02, Stephen Boyd wrote:
> Obscuring the pointers that slub shows when debugging makes for some
> confusing slub debug messages:
>
> Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17
>
> Those addresses are hashed for kernel security reasons. If we're trying
> to be secure with slub_debug on the commandline we have some big
> problems given that we dump whole chunks of kernel memory to the kernel
> logs. Let's force on the no_hash_pointers commandline flag when
> slub_debug is on the commandline. This makes slub debug messages more
> meaningful and if by chance a kernel address is in some slub debug
> object dump we will have a better chance of figuring out what went
> wrong.
>
> Note that we don't use %px in the slub code because we want to reduce
> the number of places that %px is used in the kernel. This also nicely
> prints a big fat warning at kernel boot if slub_debug is on the
> commandline so that we know that this kernel shouldn't be used on
> production systems.
>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Best Regards,
Petr
next prev parent reply other threads:[~2021-06-03 13:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-01 18:21 [PATCH v3 0/4] slub: Print non-hashed pointers in slub debugging Stephen Boyd
2021-06-01 18:21 ` [PATCH v3 1/4] slub: Restore slub_debug=- behavior Stephen Boyd
2021-06-01 18:22 ` [PATCH v3 2/4] slub: Actually use 'message' in restore_bytes() Stephen Boyd
2021-06-01 18:22 ` [PATCH v3 3/4] slub: Indicate slab_fix() uses printf formats Stephen Boyd
2021-06-06 0:06 ` David Rientjes
2021-06-01 18:22 ` [PATCH v3 4/4] slub: Force on no_hash_pointers when slub_debug is enabled Stephen Boyd
2021-06-01 22:45 ` kernel test robot
2021-06-02 0:26 ` Andrew Morton
2021-06-02 1:03 ` Stephen Boyd
2021-06-02 10:48 ` Vlastimil Babka
2021-06-02 10:50 ` Vlastimil Babka
2021-06-03 13:15 ` Petr Mladek [this message]
2021-09-20 14:29 ` Kees Cook
2021-09-20 18:23 ` Stephen Boyd
2021-09-20 18:28 ` Kees Cook
2021-09-20 18:44 ` Stephen Boyd
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