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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id w4-20020a17090a6b8400b0020d6fc00072sm11241693pjj.9.2022.10.18.02.07.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Oct 2022 02:07:07 -0700 (PDT) From: Kees Cook To: Al Viro Cc: Kees Cook , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] coredump: Proactively round up to kmalloc bucket size Date: Tue, 18 Oct 2022 02:07:05 -0700 Message-Id: <20221018090701.never.996-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1213; h=from:subject:message-id; bh=p+MmonEVAKFmpb5iqSHacNcvTbIa15T8BRPfROxVUy8=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBjTmy5m8JCx9/BE56DDkyWbIsGqGD7nmhWHa2GZ8l+ Hy6FbFKJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCY05suQAKCRCJcvTf3G3AJnEsEA CScUD9FTn1d8hXufUPd/FUQzE357ebRSIeX+m2v0ED9JXLrqJmh1gZrjrKHLkKiHTSnAn/jgoD2dgW U/YOQFrV7yyoQ4kKZzShL7FQ0s1Kki5m9LIqY/0HwPR8+tkdVVoG9a1PJoy3TBtZBDSTBQyojqxd0X Du2BbO4D0kz4QxdO1Zwl5lldGIOh7poGa2tmqXjvxG55wMNBP4WyRTNS5Id5ZMVNW2qOS0yN3rF+ac HT2LfblPNvdimyrWPwhl/2C6Ae+75yrDwn4P3d5DncHEDWBLrCqAXG5tOl2M2fLXjp7aBDKCn9t84Z yI5N3lIzvVqgzmFoQg9Z1WPlj0LmmJv49Pd/3FEGHrFdAeq4q4cKUJjclOyHapGm+NvcmkVvJWk4FU +jEB83ZhUMSqNUBe+ck7MRnOTSjsK+dJ5cau90wJyEpods3antluvAuYwQLpZxjLF+M4HvNSpJGVIE HNFPx13lmOsyt2MVaIQdGy7sm1yi8zfE/1DnLogCFzRasB3JoVBh012nXOhnl4dF0o49scKZrY1cge DGhZ0pVgCpql0gGtmm2Abphd95b4ufD7Np9gAWqH2xgvsGGicJEtY15OqOv/r61tRSwp5ieebceKfX PIOt9137ZR+Rxj7a4MQ+iIpvMA+gJDGhPYdlPr3J6MHr0kpiM4ZLE3QyUOZw== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Instead of discovering the kmalloc bucket size _after_ allocation, round up proactively so the allocation is explicitly made for the full size, allowing the compiler to correctly reason about the resulting size of the buffer through the existing __alloc_size() hint. Cc: Alexander Viro Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Kees Cook --- fs/coredump.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 7bad7785e8e6..97eaee325251 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -68,7 +68,10 @@ struct core_name { static int expand_corename(struct core_name *cn, int size) { - char *corename = krealloc(cn->corename, size, GFP_KERNEL); + char *corename; + + size = kmalloc_size_roundup(size); + corename = krealloc(cn->corename, size, GFP_KERNEL); if (!corename) return -ENOMEM; @@ -76,7 +79,7 @@ static int expand_corename(struct core_name *cn, int size) if (size > core_name_size) /* racy but harmless */ core_name_size = size; - cn->size = ksize(corename); + cn->size = size; cn->corename = corename; return 0; }