linux-kernel - Re: [PATCH v2] lsm: check size of writes

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Message-ID: <CAHC9VhTUZjsVwO874oW2+6eNYdsudUcnP_ZFGn6ZEFS1O7zk2w@mail.gmail.com>
Date: Sat, 4 Jan 2025 22:51:43 -0500
From: Paul Moore <paul@...l-moore.com>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: Leo Stone <leocstone@...il.com>, mortonm@...omium.org, 
	syzbot+4eb7a741b3216020043a@...kaller.appspotmail.com, jmorris@...ei.org, 
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, 
	serge@...lyn.com, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH v2] lsm: check size of writes

On Sat, Dec 21, 2024 at 5:01 AM Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> On 2024/12/19 6:51, Paul Moore wrote:
> > On Tue, Dec 17, 2024 at 1:27 PM Leo Stone <leocstone@...il.com> wrote:
> >>
> >> syzbot attempts to write a buffer with a large size to a sysfs entry
> >> with writes handled by handle_policy_update(), triggering a warning
> >> in kmalloc.
> >>
> >> Check the size specified for write buffers before allocating.
> >>
> >> Reported-by: syzbot+4eb7a741b3216020043a@...kaller.appspotmail.com
> >> Closes: https://syzkaller.appspot.com/bug?extid=4eb7a741b3216020043a
> >> Signed-off-by: Leo Stone <leocstone@...il.com>
> >> ---
> >> v2: Make the check in handle_policy_update() to also cover
> >> safesetid_uid_file_write(). Thanks for your feedback.
> >> v1: https://lore.kernel.org/all/20241216030213.246804-2-leocstone@gmail.com/
> >> ---
> >>  security/safesetid/securityfs.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >
> > Looks okay to me.  Micah, are you planning to merge this patch, or
> > would you like me to take it via the LSM tree?
> >
> > Reviewed-by: Paul Moore <paul@...l-moore.com>
> >
> > I'm going to tag this to come back to it in a week or so in case we
> > don't hear from Micah, but if you don't see any further replies Leo,
> > feel free to send a gentle nudge ;)
>
> FYI: I sent
>
> https://lkml.kernel.org/r/014cd694-cc27-4a07-a34a-2ae95d744515@I-love.SAKURA.ne.jp
>
> which makes this patch redundant if my patch is accepted.

Sure, but this patch is trivial, and there is no way the
KMALLOC_MAX_SIZE is limiting any normal use of safesetid so it seems
safe to apply now.  We can always revisit this change in the future
depending on how the rest of the kernel changes.

-- 
paul-moore.com