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From: Andrew Morton <akpm@linux-foundation.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH (repost)] umh: fix refcount underflow in fork_usermode_blob().
Date: Sat, 28 Mar 2020 17:55:12 -0700	[thread overview]
Message-ID: <20200328175512.e89ff65333e6c65fea211c12@linux-foundation.org> (raw)
In-Reply-To: <9b846b1f-a231-4f09-8c37-6bfb0d1e7b05@i-love.sakura.ne.jp>

On Fri, 27 Mar 2020 09:51:34 +0900 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:

> Since free_bprm(bprm) always calls allow_write_access(bprm->file) and
> fput(bprm->file) if bprm->file is set to non-NULL, __do_execve_file()
> must call deny_write_access(file) and get_file(file) if called from
> do_execve_file() path. Otherwise, use-after-free access can happen at
> fput(file) in fork_usermode_blob().
> 
>   general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC
>   CPU: 3 PID: 4131 Comm: insmod Tainted: G           O      5.6.0-rc5+ #978
>   Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019
>   RIP: 0010:fork_usermode_blob+0xaa/0x190

This is rather old code - what casued this to be observed now?  Some
unusual userspace behaviour?



  reply	other threads:[~2020-03-29  0:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-12 13:43 [PATCH] umh: fix refcount underflow in fork_usermode_blob() Tetsuo Handa
2020-03-12 14:38 ` Al Viro
2020-03-13  9:46   ` Tetsuo Handa
2020-03-20 10:31     ` Tetsuo Handa
2020-03-27  0:51       ` [PATCH (repost)] " Tetsuo Handa
2020-03-29  0:55         ` Andrew Morton [this message]
2020-03-29  4:28           ` Tetsuo Handa
2020-03-29  3:17         ` Al Viro

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