On Fri, May 17, 2024 at 10:54:20AM -0400, Kenton Groombridge wrote: > req->n_channels must be set before req->channels[] can be used. > > This patch fixes one of the issues encountered in [1]. > > [ 83.964252] ------------[ cut here ]------------ > [ 83.964255] UBSAN: array-index-out-of-bounds in net/mac80211/scan.c:364:4 > [ 83.964258] index 0 is out of range for type 'struct ieee80211_channel *[]' > [ 83.964260] CPU: 0 PID: 1695 Comm: iwd Tainted: G O T 6.8.9-gentoo-hardened1 #1 > [ 83.964262] Hardware name: System76 Pangolin/Pangolin, BIOS ARB928_V00.01_T0025ASY1_ms 04/20/2023 > [ 83.964264] Call Trace: > [ 83.964267] <TASK> > [ 83.964269] dump_stack_lvl+0x3f/0xc0 > [ 83.964274] __ubsan_handle_out_of_bounds+0xec/0x110 > [ 83.964278] ieee80211_prep_hw_scan+0x2db/0x4b0 > [ 83.964281] __ieee80211_start_scan+0x601/0x990 > [ 83.964284] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964287] ? cfg80211_scan+0x149/0x250 > [ 83.964291] nl80211_trigger_scan+0x874/0x980 > [ 83.964295] genl_family_rcv_msg_doit+0xe8/0x160 > [ 83.964298] genl_rcv_msg+0x240/0x270 > [ 83.964301] ? __cfi_nl80211_trigger_scan+0x10/0x10 > [ 83.964302] ? __cfi_nl80211_post_doit+0x10/0x10 > [ 83.964304] ? __cfi_nl80211_pre_doit+0x10/0x10 > [ 83.964307] ? __cfi_genl_rcv_msg+0x10/0x10 > [ 83.964309] netlink_rcv_skb+0x102/0x130 > [ 83.964312] genl_rcv+0x23/0x40 > [ 83.964314] netlink_unicast+0x23b/0x340 > [ 83.964316] netlink_sendmsg+0x3a9/0x450 > [ 83.964319] __sys_sendto+0x3ae/0x3c0 > [ 83.964324] __x64_sys_sendto+0x21/0x40 > [ 83.964326] do_syscall_64+0x90/0x150 > [ 83.964329] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964331] ? syscall_exit_work+0xc2/0xf0 > [ 83.964333] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964335] ? syscall_exit_to_user_mode+0x74/0xa0 > [ 83.964337] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964339] ? do_syscall_64+0x9c/0x150 > [ 83.964340] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964342] ? syscall_exit_to_user_mode+0x74/0xa0 > [ 83.964344] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964346] ? do_syscall_64+0x9c/0x150 > [ 83.964347] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964349] ? do_syscall_64+0x9c/0x150 > [ 83.964351] ? srso_alias_return_thunk+0x5/0xfbef5 u> [ 83.964353] ? syscall_exit_work+0xc2/0xf0 > [ 83.964354] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964356] ? syscall_exit_to_user_mode+0x74/0xa0 > [ 83.964358] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964359] ? do_syscall_64+0x9c/0x150 > [ 83.964361] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964362] ? do_user_addr_fault+0x488/0x620 > [ 83.964366] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964367] ? srso_alias_return_thunk+0x5/0xfbef5 > [ 83.964369] entry_SYSCALL_64_after_hwframe+0x55/0x5d > [ 83.964372] RIP: 0033:0x6200808578d7 > [ 83.964374] Code: 00 00 90 f3 0f 1e fa 41 56 55 41 89 ce 48 83 ec 28 80 3d 7b f7 0d 00 00 74 29 45 31 c9 45 31 c0 41 89 ca b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 71 48 83 c4 28 5d 41 5e c3 66 0f 1f 84 00 00 > [ 83.964375] RSP: 002b:0000730c4e821530 EFLAGS: 00000246 ORIG_RAX: 000000000000002c > [ 83.964378] RAX: ffffffffffffffda RBX: 000006dbc456c570 RCX: 00006200808578d7 > [ 83.964379] RDX: 000000000000005c RSI: 000006dbc45884f0 RDI: 0000000000000004 > [ 83.964381] RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 > [ 83.964382] R10: 0000000000000000 R11: 0000000000000246 R12: 000006dbc456c480 > [ 83.964383] R13: 000006dbc456c450 R14: 0000000000000000 R15: 000006dbc456c610 > [ 83.964386] </TASK> > [ 83.964386] ---[ end trace ]--- > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=218810 > > v1->v2: > - Drop changes in cfg80211 as requested by Johannes > > Co-authored-by: Kees Cook <keescook@xxxxxxxxxxxx> > Signed-off-by: Kenton Groombridge <concord@xxxxxxxxxx> Thanks Kenton, FWWIW, it seems unfortunate to me that the __counted_by field (n_channels) is set some distance away from the allocation of the flex-array (channels) whose bounds it checks. It seems it would be pretty easy for a bug in the code being updated here to result in an overrun. But in any case, I think this is an improvement and seems correct to me. Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
