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Wed, 24 Jan 2024 11:59:31 -0800 (PST) MIME-Version: 1.0 References: <20240124192228.work.788-kees@kernel.org> In-Reply-To: <20240124192228.work.788-kees@kernel.org> From: Jann Horn Date: Wed, 24 Jan 2024 20:58:55 +0100 Message-ID: Subject: Re: [PATCH] exec: Check __FMODE_EXEC instead of in_execve for LSMs To: Kees Cook Cc: Josh Triplett , Kevin Locke , Linus Torvalds , John Johansen , Paul Moore , James Morris , "Serge E. Hallyn" , Kentaro Takeda , Tetsuo Handa , Alexander Viro , Christian Brauner , Jan Kara , Eric Biederman , Andrew Morton , Sebastian Andrzej Siewior , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 81F414000B X-Stat-Signature: sawuaocm5f6qedhqx8wtijcmig4aecg7 X-Rspam-User: X-HE-Tag: 1706126373-537144 X-HE-Meta: U2FsdGVkX198OcTim9ehWd5co6GwKR9zYAQQNUqU3ODggozFqYVXnq0B4Msk6cv2N5swRr/jbDZkMTjN1sqFOzO+hSoPwt7tzEeMIYy0VwPv/U9ak+F+MsErfop45QnWDz6KX/NoubdrkxySoQLp2rVyvh15SZdn94zjzPrSIh3NKgnRq1++N50akwzqyqr0OXt7VQ4jTwgJO+sg1hpePTloxfVqyOSz2HBURN2IGvSf/W/S7bxwJXBbUAbNoZFsLWxg4G6JaCIBNFcK0WctMsb2RUy2NkWF5ai9wKEdxGQG/7UCADiPFgFIzfjjPLuW/rPdU98Fa394K57r5pV/QaPaTrK3lrlB4wALvc3UcN/g3qcCwY80VG6tVFqdFKCRduxkSKabWsloeWcR3ksJaJMaj/3QzxaLDGUIhPRgTeAVIhQlg7WoJWd/XH8bDWzlgvI9R4ys0PPo55zfBaBqdDI4v6n/pkSt7ZJHpH6dJxTjkEXsUPBIHvZQ8fijx09gVEqOUenKKfl+RMXZGFoFa7IauLkXGVfubkUSNwb7mXtct2VSDyatpZlvCz7vFHLgI5G5+xVzJsS2q8m4ZYS+lVFCQRTZZuhgG7/birRDalUzZHg2CpLDMjmU4mYqKk94gQHjCT/pC7NDRi3But2j7SiuZ1yvZ+bUuIQ+LKTBtnoGwrTYmk6hUL8y7uB8PqNSKq0722/LIPAVEPx83o0GBVyRynVNuMuXHlhaYu69egZmdexgjmsutA3vvMMBAOnW/mumrmXoARQcBpVC/Xg28k7WMnQw1cNiKTzWRflw0LSUebbrxY/CoEnTWylK7zUQV8+jrFkAMCEn2EQ5Oh7hjlfLuz6DKxBsQrQ6xKqNDiIJ6ji0ssiyQToS7gb26OVS4nXMEFNNXZ9mz3HPD4LTQnPKDCItWNdivb7SQKm1zdarKQbMLQKmFtixOlMkSYyIMC7tY5f3A5xc4EleXVM Bob6dDf1 Xb/jeId2Fm+VEV84oKcXUsvNS8+QoXJ2E7EUVhA8cWivUZZf20b7zm39jmoF1z2bj/B0851EB7+u+X5YQPJ+PbC6dAh6iPgPx8Rp3xzug6skZ0w7c2mqr0VLoVgw6PlkAfUK/4AfAPDvH2hc9xGeQxJALseuVB+M7bS2UUOpmF1XIL3VEE33V9LSwB/xTzsiRFJgbmRNtZnab/PUimpJKcjuMniGUBC/YVeq4gJEuNohdW0mmvk4KLNFlB2k89XjiUIH9UAKnhNRfix/28EeLg3WGKAgcT8LnoM6/6X/8RJgUPOoQsS2PI9hE45A8NclRUYrRYsOOGJIsFTE= 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 Wed, Jan 24, 2024 at 8:22=E2=80=AFPM Kees Cook w= rote: > After commit 978ffcbf00d8 ("execve: open the executable file before > doing anything else"), current->in_execve was no longer in sync with the > open(). This broke AppArmor and TOMOYO which depend on this flag to > distinguish "open" operations from being "exec" operations. > > Instead of moving around in_execve, switch to using __FMODE_EXEC, which > is where the "is this an exec?" intent is stored. Note that TOMOYO still > uses in_execve around cred handling. I think this is wrong. When CONFIG_USELIB is enabled, the uselib() syscall will open a file with __FMODE_EXEC but without going through execve(). From what I can tell, there are no bprm hooks on this path. I don't know if it _matters_ much, given that it'll only let you read/execute stuff from files with valid ELF headers, but still.