[PATCH 64/64] fortify: Add run-time WARN for cross-field memcpy()
From: Kees Cook <hidden>
Date: 2021-07-27 21:01:52
Also in:
dri-devel, linux-hardening, linux-kbuild, linux-staging, linux-wireless, lkml, netdev
Subsystem:
fortify_source, the rest · Maintainers:
Kees Cook, Linus Torvalds
This enables the run-time checking of dynamic memcpy() and memmove() lengths, issuing a WARN when a write would exceed the size of the target field. Signed-off-by: Kees Cook <redacted> --- include/linux/fortify-string.h | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 4afd42079d3b..0d0acd959ba0 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h@@ -260,7 +260,7 @@ __FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size, * V = vulnerable to run-time overflow * */ -__FORTIFY_INLINE void fortify_memcpy_chk(__kernel_size_t size, +__FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, const size_t p_size, const size_t q_size, const size_t p_size_field,
@@ -309,13 +309,25 @@ __FORTIFY_INLINE void fortify_memcpy_chk(__kernel_size_t size, if ((p_size != (size_t)(-1) && p_size < size) || (q_size != (size_t)(-1) && q_size < size)) fortify_panic(func); + + /* + * Warn when writing beyond destination field size. Since + * flexible-arrays are considered 0 bytes, we must ignore 0 sizes + * at runtime for now. + */ + if (p_size_field && p_size != p_size_field && p_size_field < size) + return true; + + return false; } #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ p_size_field, q_size_field, op) ({ \ size_t __fortify_size = (size_t)(size); \ - fortify_memcpy_chk(__fortify_size, p_size, q_size, \ - p_size_field, q_size_field, #op); \ + WARN_ONCE(fortify_memcpy_chk(__fortify_size, p_size, q_size, \ + p_size_field, q_size_field, #op), \ + #op ": detected field-spanning write (size %zu) of single field (size %zu)\n", \ + __fortify_size, p_size_field); \ __underlying_##op(p, q, __fortify_size); \ })
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2.30.2