On Wed, Mar 31, 2021 at 04:45:34PM -0500, Gustavo A. R. Silva wrote: > Fix the following out-of-bounds warning by enclosing > some structure members into new struct req: > > arch/x86/include/asm/string_32.h:182:25: warning: '__builtin_memcpy' offset [39, 108] from the object at 'sig' is out of the bounds of referenced subobject 'beacon_period' with type 'short unsigned int' at offset 36 [-Warray-bounds] > > Refactor the code, accordingly: > > $ pahole -C wl3501_join_req drivers/net/wireless/wl3501_cs.o > struct wl3501_join_req { > u16 next_blk; /* 0 2 */ > u8 sig_id; /* 2 1 */ > u8 reserved; /* 3 1 */ > struct iw_mgmt_data_rset operational_rset; /* 4 10 */ > u16 reserved2; /* 14 2 */ > u16 timeout; /* 16 2 */ > u16 probe_delay; /* 18 2 */ > u8 timestamp[8]; /* 20 8 */ > u8 local_time[8]; /* 28 8 */ > struct { > u16 beacon_period; /* 36 2 */ > u16 dtim_period; /* 38 2 */ > u16 cap_info; /* 40 2 */ > u8 bss_type; /* 42 1 */ > u8 bssid[6]; /* 43 6 */ > struct iw_mgmt_essid_pset ssid; /* 49 34 */ > /* --- cacheline 1 boundary (64 bytes) was 19 bytes ago --- */ > struct iw_mgmt_ds_pset ds_pset; /* 83 3 */ > struct iw_mgmt_cf_pset cf_pset; /* 86 8 */ > struct iw_mgmt_ibss_pset ibss_pset; /* 94 4 */ > struct iw_mgmt_data_rset bss_basic_rset; /* 98 10 */ > } req; /* 36 72 */ This section is the same as a large portion of struct wl3501_scan_confirm: struct wl3501_scan_confirm { u16 next_blk; u8 sig_id; u8 reserved; u16 status; char timestamp[8]; char localtime[8]; from here u16 beacon_period; u16 dtim_period; u16 cap_info; u8 bss_type; u8 bssid[ETH_ALEN]; struct iw_mgmt_essid_pset ssid; struct iw_mgmt_ds_pset ds_pset; struct iw_mgmt_cf_pset cf_pset; struct iw_mgmt_ibss_pset ibss_pset; struct iw_mgmt_data_rset bss_basic_rset; through here u8 rssi; }; It seems like maybe extracting that and using it in both structures would make more sense? > > /* size: 108, cachelines: 2, members: 10 */ > /* last cacheline: 44 bytes */ > }; > > The problem is that the original code is trying to copy data into a > bunch of struct members adjacent to each other in a single call to > memcpy(). Now that a new struct _req_ enclosing all those adjacent > members is introduced, memcpy() doesn't overrun the length of > &sig.beacon_period, because the address of the new struct object > _req_ is used as the destination, instead. > > Also, this helps with the ongoing efforts to enable -Warray-bounds and > avoid confusing the compiler. > > Link: https://github.com/KSPP/linux/issues/109 > Reported-by: kernel test robot <lkp@xxxxxxxxx> > Build-tested-by: kernel test robot <lkp@xxxxxxxxx> > Link: https://lore.kernel.org/lkml/60641d9b.2eNLedOGSdcSoAV2%25lkp@xxxxxxxxx/ > Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> > --- > Changes in v2: > - None. > > drivers/net/wireless/wl3501.h | 22 ++++++++++++---------- > drivers/net/wireless/wl3501_cs.c | 4 ++-- > 2 files changed, 14 insertions(+), 12 deletions(-) > > diff --git a/drivers/net/wireless/wl3501.h b/drivers/net/wireless/wl3501.h > index ef9d605d8c88..774d8cac046d 100644 > --- a/drivers/net/wireless/wl3501.h > +++ b/drivers/net/wireless/wl3501.h > @@ -389,16 +389,18 @@ struct wl3501_join_req { > u16 probe_delay; > u8 timestamp[8]; > u8 local_time[8]; > - u16 beacon_period; > - u16 dtim_period; > - u16 cap_info; > - u8 bss_type; > - u8 bssid[ETH_ALEN]; > - struct iw_mgmt_essid_pset ssid; > - struct iw_mgmt_ds_pset ds_pset; > - struct iw_mgmt_cf_pset cf_pset; > - struct iw_mgmt_ibss_pset ibss_pset; > - struct iw_mgmt_data_rset bss_basic_rset; > + struct { > + u16 beacon_period; > + u16 dtim_period; > + u16 cap_info; > + u8 bss_type; > + u8 bssid[ETH_ALEN]; > + struct iw_mgmt_essid_pset ssid; > + struct iw_mgmt_ds_pset ds_pset; > + struct iw_mgmt_cf_pset cf_pset; > + struct iw_mgmt_ibss_pset ibss_pset; > + struct iw_mgmt_data_rset bss_basic_rset; > + } req; > }; > > struct wl3501_join_confirm { > diff --git a/drivers/net/wireless/wl3501_cs.c b/drivers/net/wireless/wl3501_cs.c > index e149ef81d6cc..399d3bd2ae76 100644 > --- a/drivers/net/wireless/wl3501_cs.c > +++ b/drivers/net/wireless/wl3501_cs.c > @@ -590,7 +590,7 @@ static int wl3501_mgmt_join(struct wl3501_card *this, u16 stas) > struct wl3501_join_req sig = { > .sig_id = WL3501_SIG_JOIN_REQ, > .timeout = 10, > - .ds_pset = { > + .req.ds_pset = { > .el = { > .id = IW_MGMT_INFO_ELEMENT_DS_PARAMETER_SET, > .len = 1, > @@ -599,7 +599,7 @@ static int wl3501_mgmt_join(struct wl3501_card *this, u16 stas) > }, > }; > > - memcpy(&sig.beacon_period, &this->bss_set[stas].beacon_period, 72); > + memcpy(&sig.req, &this->bss_set[stas].beacon_period, sizeof(sig.req)); If not, then probably something like this should be added to make sure nothing unexpected happens to change structure sizes: BUILD_BUG_ON(sizeof(sig.req) != 72); > return wl3501_esbq_exec(this, &sig, sizeof(sig)); > } > > -- > 2.27.0 > -- Kees Cook