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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z20-20020a630a54000000b003c219c0871asm3933040pgk.74.2022.05.03.13.55.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 May 2022 13:55:08 -0700 (PDT) From: Kees Cook To: Bill Wendling Cc: Kees Cook , David Howells , Jeff Layton , Masahiro Yamada , Nick Desaulniers , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-hardening@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH 1/6] netfs: Eliminate Clang randstruct warning Date: Tue, 3 May 2022 13:54:58 -0700 Message-Id: <20220503205503.3054173-2-keescook@chromium.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220503205503.3054173-1-keescook@chromium.org> References: <20220503205503.3054173-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1970; h=from:subject; bh=bEl5c+oL0DHs9c0JKOjQVQhGUtntych2+mEKBNpt6+0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBicZaljMui7HM5C2nUhMVbY5QZL7cXs2WS/tnBqO2w QmtevbyJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYnGWpQAKCRCJcvTf3G3AJj7nD/ 9EN/kMgbEYlp++FHvHW8ma1iM+kP7FMs+DalBiKQfkIeScig0IVM5Q3dbvmXF1a26tX7uVVdilImNn hZvggBQj2ca6FXKUR60ZWvagiS3PrqNy/RdFhO4F29yx6c6gWrFJmsx2c25jJ1sJXp5sx6onOD64Dc eLXJPFVDQrMssMfu9+SQCRfcf3SDsKHcV5PRjOp5aiWqKI9yR6dWUheY3Sa4bsBYn645OAdQI93Z5k kmYosamsbYqGm9Xa2wWXalmB3W9x5Licr6O86aeeCfhuL8q12lrebTGwLo2PwpigLCbIgHrxSqJXIn stPRkOoWqNufv4kkQbewUAitGsMC6vT/2o7MylXDzRnKJujUZQY5wRBekBslXliKHtkxBb6ZGF8RQU fmbUaDHA9aKUMgMVHjzacxPBbJPV7oycgCPiRwbOBOmJNg3sYJQ0Y306ki6v+dOHLcj7wedfcPM0OU uolaHrzpi63qdj96tcn1R6hMdI166zDodVrQQ+NERYFJkdvfL7eSA+a6nfJ1GhI8W7R6HKS7CcJ+Xg Jj+pEWxNzyJ2Ee+WfxBM1qdcLOfVN64qrjDWaK0A6LKoH+NVZUbT5pYEv2eoow+Rll6b+uSLhDaqWX uVOm6X9q1dBcMoZx5a3JgZpzg9B8yHotQF8ovOWc5X15GHixJg4Er4sXOCkg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Clang's structure layout randomization feature gets upset when it sees struct inode (which is randomized) cast to struct netfs_i_context. This is due to seeing the inode pointer as being treated as an array of inodes, rather than "something else, following struct inode". Since netfs can't use container_of() (since it doesn't know what the true containing struct is), it uses this direct offset instead. Adjust the code to better reflect what is happening: an arbitrary pointer is being adjusted and cast to something else: use a "void *" for the math. The resulting binary output is the same, but Clang no longer sees an unexpected cross-structure cast: In file included from ../fs/nfs/inode.c:50: In file included from ../fs/nfs/fscache.h:15: In file included from ../include/linux/fscache.h:18: ../include/linux/netfs.h:298:9: error: casting from randomized structure pointer type 'struct inode *' to 'struct netfs_i_context *' return (struct netfs_i_context *)(inode + 1); ^ 1 error generated. Cc: David Howells Cc: Jeff Layton Signed-off-by: Kees Cook Reviewed-by: Jeff Layton --- include/linux/netfs.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/netfs.h b/include/linux/netfs.h index c7bf1eaf51d5..0c33b715cbfd 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -295,7 +295,7 @@ extern void netfs_stats_show(struct seq_file *); */ static inline struct netfs_i_context *netfs_i_context(struct inode *inode) { - return (struct netfs_i_context *)(inode + 1); + return (void *)inode + sizeof(*inode); } /** @@ -307,7 +307,7 @@ static inline struct netfs_i_context *netfs_i_context(struct inode *inode) */ static inline struct inode *netfs_inode(struct netfs_i_context *ctx) { - return ((struct inode *)ctx) - 1; + return (void *)ctx - sizeof(struct inode); } /**