wl3501_cs: Fix out-of-bounds warnings in wl3501_send_pkt
authorGustavo A. R. Silva <gustavoars@kernel.org>
Wed, 14 Apr 2021 23:43:19 +0000 (18:43 -0500)
committerKalle Valo <kvalo@codeaurora.org>
Thu, 22 Apr 2021 14:38:36 +0000 (17:38 +0300)
commit820aa37638a252b57967bdf4038a514b1ab85d45
tree228d0793382f8c117b3b6c7d0f5aff50b543afab
parentff9f732a87caa5f7bab72bea3aaad58db9b1ac60
wl3501_cs: Fix out-of-bounds warnings in wl3501_send_pkt

Fix the following out-of-bounds warnings by enclosing structure members
daddr and saddr into new struct addr, in structures wl3501_md_req and
wl3501_md_ind:

arch/x86/include/asm/string_32.h:182:25: warning: '__builtin_memcpy' offset [18, 23] from the object at 'sig' is out of the bounds of referenced subobject 'daddr' with type 'u8[6]' {aka 'unsigned char[6]'} at offset 11 [-Warray-bounds]
arch/x86/include/asm/string_32.h:182:25: warning: '__builtin_memcpy' offset [18, 23] from the object at 'sig' is out of the bounds of referenced subobject 'daddr' with type 'u8[6]' {aka 'unsigned char[6]'} at offset 11 [-Warray-bounds]

Refactor the code, accordingly:

$ pahole -C wl3501_md_req drivers/net/wireless/wl3501_cs.o
struct wl3501_md_req {
u16                        next_blk;             /*     0     2 */
u8                         sig_id;               /*     2     1 */
u8                         routing;              /*     3     1 */
u16                        data;                 /*     4     2 */
u16                        size;                 /*     6     2 */
u8                         pri;                  /*     8     1 */
u8                         service_class;        /*     9     1 */
struct {
u8                 daddr[6];             /*    10     6 */
u8                 saddr[6];             /*    16     6 */
} addr;                                          /*    10    12 */

/* size: 22, cachelines: 1, members: 8 */
/* last cacheline: 22 bytes */
};

$ pahole -C wl3501_md_ind drivers/net/wireless/wl3501_cs.o
struct wl3501_md_ind {
u16                        next_blk;             /*     0     2 */
u8                         sig_id;               /*     2     1 */
u8                         routing;              /*     3     1 */
u16                        data;                 /*     4     2 */
u16                        size;                 /*     6     2 */
u8                         reception;            /*     8     1 */
u8                         pri;                  /*     9     1 */
u8                         service_class;        /*    10     1 */
struct {
u8                 daddr[6];             /*    11     6 */
u8                 saddr[6];             /*    17     6 */
} addr;                                          /*    11    12 */

/* size: 24, cachelines: 1, members: 9 */
/* padding: 1 */
/* last cacheline: 24 bytes */
};

The problem is that the original code is trying to copy data into a
couple of arrays adjacent to each other in a single call to memcpy().
Now that a new struct _addr_ enclosing those two adjacent arrays
is introduced, memcpy() doesn't overrun the length of &sig.daddr[0]
and &sig.daddr, because the address of the new struct object _addr_
is used, instead.

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/d260fe56aed7112bff2be5b4d152d03ad7b78e78.1618442265.git.gustavoars@kernel.org
drivers/net/wireless/wl3501.h
drivers/net/wireless/wl3501_cs.c