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b=tNbZ3asG1h+6NzR3gqFiEzc9uHqZKts3ieC9wbv7XJJhABcQaRwcERAmfisEEbzbw KolyAPJk7xHHKrq3H0qp3S5z2eQ6Isff96dCX6ASIkb3b+bfa5Hw04mLeOzlsF+6Wa CEd2P3VjBIFwbeY2nD3/unii4yee7O7yIb6d3f7az5tDmKiASMcnHSdqUUw3AduWbr jvRu12juB64C5a0r2l6VAoT9zClsTUK2Qrbb84feV6yBdw9O7SalWTODGKVri30ywX b1zbF5k/d8klmpeNuMM3onVDGAMMAL7IAdixxB/TVdX+dvtPDV5IPI4mb4Vo775IAj 9WxJ8dnLpRIVw== Date: Fri, 21 Jun 2024 00:00:06 -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: <202406202354.3020C4FCA4@keescook> References: <20240520021337.work.198-kees@kernel.org> <20240520021615.741800-2-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 9sye6sx4fxyamocnj5dr83ryewc38m41 X-Rspam-User: X-Rspamd-Queue-Id: 2583D160024 X-Rspamd-Server: rspam02 X-HE-Tag: 1718953207-35513 X-HE-Meta: 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 YlYvHAno 9IhHj8dZnZvoKqMSg+8XH6joZT7YjWRleCW/djmfL3uv3TR9HqK68fDZztGwWhekj60ilRhvfBCJzjms99V29iXDn1/vOje91u0759rvryLpgRwJPpojizhyDaKay4XM9Ud4swdDZQkEoK5xGS6AwbXAEE3I8tTR3PO81kJwHIGnJeLZ42Gngw2tnhebUA1NV38uvzMv4dc9Uoqd7Jqpa9XHzH6E0Zp+2YsQDW1Q0UqOaLgQfn6YMJBsrxrILXZ+NgCz4k6KQJO3OM56e7Molw9Er3w== 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 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; -- Kees Cook