fortify: Fix incorrect reporting of read buffer size

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")
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20250729231817.work.023-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index e4ce1ca..b3b53f8 100644 (file)
--- 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.