s390/zcrypt: Switch to flexible array member

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally reading/writing across neighboring array fields.

Switch from zero-element arrays to flexible arrays so the compiler will
perform appropriate bounds checking, avoiding these future warnings:

In function '__fortify_memcpy',
    inlined from 'cca_sec2protkey' at drivers/s390/crypto/zcrypt_ccamisc.c:645:2:
./include/linux/fortify-string.h:244:4: error: call to '__write_overflow_field' declared with attribute error: detected write beyond size of field (1st parameter)

In function '__fortify_memcpy',
    inlined from 'cca_clr2seckey' at drivers/s390/crypto/zcrypt_ccamisc.c:568:3:
./include/linux/fortify-string.h:246:4: error: call to '__read_overflow2_field' declared with attribute error: detected read beyond size of field (2nd parameter)

In function '__fortify_memcpy',
    inlined from 'cca_genseckey' at drivers/s390/crypto/zcrypt_ccamisc.c:429:2:
./include/linux/fortify-string.h:246:4: error: call to '__read_overflow2_field' declared with attribute error: detected read beyond size of field (2nd parameter)

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210616201903.1245949-1-keescook@chromium.org
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/drivers/s390/crypto/zcrypt_ccamisc.c b/drivers/s390/crypto/zcrypt_ccamisc.c
index 6a82033696e5092c921e1db033547be4146ddc0a..bc34bedf9db8b33c473a2c7bfe1dbb98f0031459 100644 (file)
--- a/drivers/s390/crypto/zcrypt_ccamisc.c
+++ b/drivers/s390/crypto/zcrypt_ccamisc.c
@@ -330,7 +330,7 @@ int cca_genseckey(u16 cardnr, u16 domain,
                        struct {
                                u16 toklen;
                                u16 tokattr;
-                               u8  tok[0];
+                               u8  tok[];
                                /* ... some more data ... */
                        } keyblock;
                } lv3;
@@ -471,7 +471,7 @@ int cca_clr2seckey(u16 cardnr, u16 domain, u32 keybitsize,
                        struct {
                                u16 toklen;
                                u16 tokattr;
-                               u8  tok[0];
+                               u8  tok[];
                                /* ... some more data ... */
                        } keyblock;
                } lv3;
@@ -596,7 +596,7 @@ int cca_sec2protkey(u16 cardnr, u16 domain,
                        u16 len;
                        u16 attr_len;
                        u16 attr_flags;
-                       u8  token[0];         /* cca secure key token */
+                       u8  token[];          /* cca secure key token */
                } lv2;
        } __packed * preqparm;
        struct uskrepparm {