From e7549481255167dcdab355c539562c7ace17e111 Mon Sep 17 00:00:00 2001 From: Jacob Keller Date: Mon, 27 Feb 2023 12:24:28 -0800 Subject: [PATCH] coccinelle: semantic patch to check for potential struct_size calls include/linux/overflow.h includes helper macros intended for calculating sizes of allocations. These macros prevent accidental overflow by saturating at SIZE_MAX. In general when calculating such sizes use of the macros is preferred. Add a semantic patch which can detect code patterns which can be replaced by struct_size. Note that I set the confidence to medium because this patch doesn't make an attempt to ensure that the relevant array is actually a flexible array. The struct_size macro does specifically require a flexible array. In many cases the detected code could be refactored to a flexible array, but this is not always possible (such as if there are multiple over-allocations). Signed-off-by: Jacob Keller Link: https://lore.kernel.org/r/20230227202428.3657443-1-jacob.e.keller@intel.com Signed-off-by: Kees Cook --- scripts/coccinelle/misc/struct_size.cocci | 74 +++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 scripts/coccinelle/misc/struct_size.cocci diff --git a/scripts/coccinelle/misc/struct_size.cocci b/scripts/coccinelle/misc/struct_size.cocci new file mode 100644 index 000000000000..9b02c37438e4 --- /dev/null +++ b/scripts/coccinelle/misc/struct_size.cocci @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only +/// +/// Check for code that could use struct_size(). +/// +// Confidence: Medium +// Author: Jacob Keller +// Copyright: (C) 2023 Intel Corporation +// Options: --no-includes --include-headers + +virtual patch +virtual context +virtual org +virtual report + +// the overflow Kunit tests have some code which intentionally does not use +// the macros, so we want to ignore this code when reporting potential +// issues. +@overflow_tests@ +identifier f = overflow_size_helpers_test; +@@ + +f + +//---------------------------------------------------------- +// For context mode +//---------------------------------------------------------- + +@depends on !overflow_tests && context@ +expression E1, E2; +identifier m; +@@ +( +* (sizeof(*E1) + (E2 * sizeof(*E1->m))) +) + +//---------------------------------------------------------- +// For patch mode +//---------------------------------------------------------- + +@depends on !overflow_tests && patch@ +expression E1, E2; +identifier m; +@@ +( +- (sizeof(*E1) + (E2 * sizeof(*E1->m))) ++ struct_size(E1, m, E2) +) + +//---------------------------------------------------------- +// For org and report mode +//---------------------------------------------------------- + +@r depends on !overflow_tests && (org || report)@ +expression E1, E2; +identifier m; +position p; +@@ +( + (sizeof(*E1)@p + (E2 * sizeof(*E1->m))) +) + +@script:python depends on org@ +p << r.p; +@@ + +coccilib.org.print_todo(p[0], "WARNING should use struct_size") + +@script:python depends on report@ +p << r.p; +@@ + +msg="WARNING: Use struct_size" +coccilib.report.print_report(p[0], msg) +