[PATCH v2] crypto: octeontx2 - Avoid stack variable overflow

[Kees Cook <keescook@chromium.org>]

Building with -Warray-bounds showed a stack variable array index
overflow. Increase the expected size of the array to avoid the warning:

In file included from ./include/linux/printk.h:555,
                 from ./include/asm-generic/bug.h:22,
                 from ./arch/x86/include/asm/bug.h:84,
                 from ./include/linux/bug.h:5,
                 from ./include/linux/mmdebug.h:5,
                 from ./include/linux/gfp.h:5,
                 from ./include/linux/firmware.h:7,
                 from drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c:5:
drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c: In function 'otx2_cpt_print_uc_dbg_info':
./include/linux/dynamic_debug.h:162:33: warning: array subscript 4 is above array bounds of 'u32[4]' {aka 'unsigned int[4]'} [-Warray-bounds]
  162 |         _dynamic_func_call(fmt, __dynamic_pr_debug,             \
      |                                 ^
./include/linux/dynamic_debug.h:134:17: note: in definition of macro '__dynamic_func_call'
  134 |                 func(&id, ##__VA_ARGS__);               \
      |                 ^~~~
./include/linux/dynamic_debug.h:162:9: note: in expansion of macro '_dynamic_func_call'
  162 |         _dynamic_func_call(fmt, __dynamic_pr_debug,             \
      |         ^~~~~~~~~~~~~~~~~~
./include/linux/printk.h:570:9: note: in expansion of macro 'dynamic_pr_debug'
  570 |         dynamic_pr_debug(fmt, ##__VA_ARGS__)
      |         ^~~~~~~~~~~~~~~~
drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c:1807:41: note: in expansion of macro 'pr_debug'
 1807 |                                         pr_debug("Mask: %8.8x %8.8x %8.8x %8.8x %8.8x",
      |                                         ^~~~~~~~
drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c:1765:13: note: while referencing 'mask'
 1765 |         u32 mask[4];
      |             ^~~~

This is justified because the mask size (eng_grps->engs_num) can be at
most 144 (OTX2_CPT_MAX_ENGINES bits), which is larger than available
storage. 4 * 32 == 128, so this must be 5: 5 * 32bit = 150.

Additionally clear the mask before conversion so trailing bits are zero.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Boris Brezillon <bbrezillon@kernel.org>
Cc: Arnaud Ebalard <arno@natisbad.org>
Cc: Srujana Challa <schalla@marvell.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Suheil Chandran <schandran@marvell.com>
Cc: Shijith Thotton <sthotton@marvell.com>
Cc: Lukasz Bartosik <lbartosik@marvell.com>
Cc: linux-crypto@vger.kernel.org
Fixes: d9d7749773e8 ("crypto: octeontx2 - add apis for custom engine groups")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v1: https://lore.kernel.org/lkml/20211215225558.1995027-1-keescook@chromium.org/
v2:
 - expliticly zero "mask"
 - explain math in commit log
 - move definition into local context
---
 drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c b/drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c
index 4c8ebdf671ca..1b4d425bbf0e 100644
--- a/drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c
+++ b/drivers/crypto/marvell/octeontx2/otx2_cptpf_ucode.c
@@ -1753,7 +1753,6 @@ void otx2_cpt_print_uc_dbg_info(struct otx2_cptpf_dev *cptpf)
 	char engs_info[2 * OTX2_CPT_NAME_LENGTH];
 	struct otx2_cpt_eng_grp_info *grp;
 	struct otx2_cpt_engs_rsvd *engs;
-	u32 mask[4];
 	int i, j;
 
 	pr_debug("Engine groups global info");
@@ -1785,6 +1784,8 @@ void otx2_cpt_print_uc_dbg_info(struct otx2_cptpf_dev *cptpf)
 		for (j = 0; j < OTX2_CPT_MAX_ETYPES_PER_GRP; j++) {
 			engs = &grp->engs[j];
 			if (engs->type) {
+				u32 mask[5] = { };
+
 				get_engs_info(grp, engs_info,
 					      2 * OTX2_CPT_NAME_LENGTH, j);
 				pr_debug("Slot%d: %s", j, engs_info);
-- 
2.30.2