linux-kernel - Re: [PATCH net-next] bpf: avoid copying junk bytes in bpf_get_current

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20160309.232812.952849846092100551.davem@davemloft.net>
Date:	Wed, 09 Mar 2016 23:28:12 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ast@...com
Cc:	daniel@...earbox.net, tobias@...dekranz.com,
	brendan.d.gregg@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH net-next] bpf: avoid copying junk bytes in
 bpf_get_current_comm()

From: Alexei Starovoitov <ast@...com>
Date: Wed, 9 Mar 2016 20:02:33 -0800

> Lots of places in the kernel use memcpy(buf, comm, TASK_COMM_LEN); but
> the result is typically passed to print("%s", buf) and extra bytes
> after zero don't cause any harm.
> In bpf the result of bpf_get_current_comm() is used as the part of
> map key and was causing spurious hash map mismatches.
> Use strlcpy() to guarantee zero-terminated string.
> bpf verifier checks that output buffer is zero-initialized,
> so even for short task names the output buffer don't have junk bytes.
> Note it's not a security concern, since kprobe+bpf is root only.
> 
> Fixes: ffeedafbf023 ("bpf: introduce current->pid, tgid, uid, gid, comm accessors")
> Reported-by: Tobias Waldekranz <tobias@...dekranz.com>
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> ---
> Targeting net-next, since it's too late for net.
> I think it makes sense for stable as well.

Applied and queued up for -stable, thanks.