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R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 53/82] fs: Refactor intentional wrap-around test Date: Mon, 22 Jan 2024 16:27:28 -0800 Message-Id: <20240123002814.1396804-53-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1854; i=keescook@chromium.org; h=from:subject; bh=nfo7Pn+Yi1zHl6gAcNSHg7VhEroNaouSkiXnEe5ME0I=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgJNnJ/s6Wgv/6AhsrzLX4ud+nwKsZVT6phE 9TF2kTHZzqJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8ICQAKCRCJcvTf3G3A JqgLD/9/8tepsjDo0cRyL40X6tIYA+MlThX9khW3Oe3bkhpOGQukol41PQ55NX8DKADGKtJeVXE zid5B46i5QDXe4vObMddWL03qTDHEu+NBMnj6IS1gcFy+ACV8M9LiMAjU+pEhRxIO7/NpMLI68u +AvCayzHQGjHq1qTfG2nYMi4TLZ9cRFbeZIun8kIm1YGDXWBctkqy3INiE/sR5MPcNpkAmIFxNz 1dKrxf1i211L4BkQyoO/InMUKRrYVDF78PVzluyJTqSgLEc9D5qCcI+Vo0VaBO0R75DEIiOHfY5 EViF1CVo/kpW4J3j3IS4RJlVmPbxL2UClAa7Vg9/z5dkuosRHRTVxdcPB4z3SjJCBZ7dUo3GpAq 74GHlOV9yNPXB5VjDSPKEds9yYRy9c+44VGtmKxNAUBhCBJxwQPcb6wIcNvO27WVOZpYvbzamLc 30PjGfsUiWxGN5uukY0/ckbaiG4dAIAPEo/KMSr/hNLub8qeGb/aSDQeu6CE+XPZqzPl1xtqHj9 L7vkoaCthNao7p9MqU/e6qIIXd8gDyd4llaE0p2GQBBzc+FTEiugOeUj8qUCemSX2UK9Ykiy0Rt 1tlwqyKloM/PgeSniTn79DIp3Uli7PmcwSwFFwomCXODyt8mGRBPw94d4JOAshi4fsjy+LsFTua Zx1eyKoK6bRm++A== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Kees Cook Reviewed-by: Jan Kara --- fs/remap_range.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/remap_range.c b/fs/remap_range.c index f8c1120b8311..15e91bf2c5e3 100644 --- a/fs/remap_range.c +++ b/fs/remap_range.c @@ -45,7 +45,7 @@ static int generic_remap_checks(struct file *file_in, loff_t pos_in, return -EINVAL; /* Ensure offsets don't wrap. */ - if (pos_in + count < pos_in || pos_out + count < pos_out) + if (add_would_overflow(pos_in, count) || add_would_overflow(pos_out, count)) return -EINVAL; size_in = i_size_read(inode_in);