Re: [PATCH] fortify: Fix incorrect reporting of read buffer size

[Gustavo A. R. Silva]

On 29/07/25 17:18, Kees Cook wrote:

When FORTIFY_SOURCE reports about a run-time buffer overread, the wrong
buffer size was being shown in the error message. (The bounds checking
was correct.)

Fixes: 3d965b33e40d ("fortify: Improve buffer overflow reporting")
Signed-off-by: Kees Cook <k...@kernel.org>

Reviewed-by: Gustavo A. R. Silva <gustavo...@kernel.org>

Thanks!
-Gustavo

---
Cc: <linux-hardening@vger.kernel.org>
---
  include/linux/fortify-string.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index e4ce1cae03bf..b3b53f8c1b28 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -596,7 +596,7 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t 
size,
        if (p_size != SIZE_MAX && p_size < size)
                fortify_panic(func, FORTIFY_WRITE, p_size, size, true);
        else if (q_size != SIZE_MAX && q_size < size)
-               fortify_panic(func, FORTIFY_READ, p_size, size, true);
+               fortify_panic(func, FORTIFY_READ, q_size, size, true);

/*

         * Warn when writing beyond destination field size.