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b=iwNCySqlZdeszGD4B9MJnJgroEhQAAmklWeqpCDmvAN3oCw2FMLffDzm0/bqZt9Rc 45WEbirPPH5mEglpgJqGQiU0wibvyvDr4pcaN6TMxghA5Em7wlE8CplQd+CVG9CKFU 56IiRr0LFPE7AANKIrl703qDoEk3nfO/TXxBaTxb20sihW+GjX91TgsTQwbr7CpKFa C7ixhTyejfOmh1b2hJdWdtwWG5sA6aS7WUMM36mzntbJVL1gxMeuSerbougN1raodQ YnGKUK8ApMnqUyK9xTnoc8OkpnDO6TOr4yHNjYsrv3/TK367s2ns7MxBA3LUYxPfyB vxqn2yJtjCt8g== Date: Fri, 21 Jun 2024 12:54:49 -0700 From: Kees Cook To: Guenter Roeck Cc: Eric Biederman , Justin Stitt , Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 2/2] exec: Avoid pathological argc, envc, and bprm->p values Message-ID: <202406211253.7037F69@keescook> References: <20240520021337.work.198-kees@kernel.org> <20240520021615.741800-2-keescook@chromium.org> <202406202354.3020C4FCA4@keescook> <1f410012-bf41-4825-9a37-7b7cc7c1df76@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1f410012-bf41-4825-9a37-7b7cc7c1df76@roeck-us.net> X-Rspamd-Queue-Id: 2C4BD80008 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: wnxie71q1jcnno5tuxeruzrbxegb4gmj X-HE-Tag: 1718999692-842037 X-HE-Meta: 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 UMM8zKf/ l2JbhCPhVgoVL/Iy4+snRvGSirV0LKxGkcd9F3OGuIfPJ8lNvXE/6EIlZfagrUcjbmywXOhrZ52fySv5LEufRnF54So/FyBajvF3d/OMdquB64blXXSdcAYsCB3eUjpeM7GTRvcCJypr/OVHWFOsOBVjx1nVBrUVOw+RpDNEHygAOkXGUbCpkgSvthNSwEOF/CW6wkpfL/NQgjbTskj15G8kjToWjxvkZM2Bz1X7BPZRvVGBsmQn04zj/JVURLxhbhe85Rclc1QE9mDXXLmLx9blz5e+Ck+F/cnT4EuHNfqlFLcX4ZjV2nKhCbRTclQkprTYQImpZq5TzBO97LeQkPIkE6xSis6jp6o0waA3w57/sywM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jun 21, 2024 at 06:21:15AM -0700, Guenter Roeck wrote: > On 6/21/24 00:00, Kees Cook wrote: > > On Thu, Jun 20, 2024 at 05:19:55PM -0700, Guenter Roeck wrote: > > > Hi, > > > > > > On Sun, May 19, 2024 at 07:16:12PM -0700, Kees Cook wrote: > > > > Make sure nothing goes wrong with the string counters or the bprm's > > > > belief about the stack pointer. Add checks and matching self-tests. > > > > > > > > For 32-bit validation, this was run under 32-bit UML: > > > > $ tools/testing/kunit/kunit.py run --make_options SUBARCH=i386 exec > > > > > > > > Signed-off-by: Kees Cook > > > > > > With this patch in linux-next, the qemu m68k:mcf5208evb emulation > > > fails to boot. The error is: > > > > Eeek. Thanks for the report! I've dropped this patch from my for-next > > tree. > > > > > Run /init as init process > > > Failed to execute /init (error -7) > > > > -7 is E2BIG, so it's certainly one of the 3 new added checks. I must > > have made a mistake in my reasoning about how bprm->p is initialized; > > the other two checks seems extremely unlikely to be tripped. > > > > I will try to get qemu set up and take a close look at what's happening. > > While I'm doing that, if it's easy for you, can you try it with just > > this removed (i.e. the other 2 new -E2BIG cases still in place): > > > > /* Avoid a pathological bprm->p. */ > > if (bprm->p < limit) > > return -E2BIG; > > I added a printk: > > argc: 1 envc: 2 p: 262140 limit: 2097152 > ^^^^^^^^^^^^^^^^^^^^^^^^ > Removing the check above does indeed fix the problem. Thanks for checking this! And I've found my mistake. "argmin" is only valid for CONFIG_MMU. And you noticed this back in 2018. ;) http://lkml.kernel.org/r/20181126122307.GA1660@redhat.com I will try to fix this better so we don't trip over it again. -- Kees Cook