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Message-Id: <20231113.141706.1726048567891462701.syoshida@redhat.com> Date: Mon, 13 Nov 2023 14:17:06 +0900 (JST) From: Shigeru Yoshida <syoshida@...hat.com> To: horms@...nel.org Cc: jmaloy@...hat.com, ying.xue@...driver.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org, tipc-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org Subject: Re: [PATCH net] tipc: Fix kernel-infoleak due to uninitialized TLV value On Sun, 12 Nov 2023 10:25:13 +0000, Simon Horman wrote: > On Sat, Nov 11, 2023 at 01:39:47AM +0900, Shigeru Yoshida wrote: >> KMSAN reported the following kernel-infoleak issue: >> >> ===================================================== >> BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline] >> BUG: KMSAN: kernel-infoleak in copy_to_user_iter lib/iov_iter.c:24 [inline] >> BUG: KMSAN: kernel-infoleak in iterate_ubuf include/linux/iov_iter.h:29 [inline] >> BUG: KMSAN: kernel-infoleak in iterate_and_advance2 include/linux/iov_iter.h:245 [inline] >> BUG: KMSAN: kernel-infoleak in iterate_and_advance include/linux/iov_iter.h:271 [inline] >> BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x4ec/0x2bc0 lib/iov_iter.c:186 >> instrument_copy_to_user include/linux/instrumented.h:114 [inline] >> copy_to_user_iter lib/iov_iter.c:24 [inline] >> iterate_ubuf include/linux/iov_iter.h:29 [inline] >> iterate_and_advance2 include/linux/iov_iter.h:245 [inline] >> iterate_and_advance include/linux/iov_iter.h:271 [inline] >> _copy_to_iter+0x4ec/0x2bc0 lib/iov_iter.c:186 >> copy_to_iter include/linux/uio.h:197 [inline] >> simple_copy_to_iter net/core/datagram.c:532 [inline] >> __skb_datagram_iter.5+0x148/0xe30 net/core/datagram.c:420 >> skb_copy_datagram_iter+0x52/0x210 net/core/datagram.c:546 >> skb_copy_datagram_msg include/linux/skbuff.h:3960 [inline] >> netlink_recvmsg+0x43d/0x1630 net/netlink/af_netlink.c:1967 >> sock_recvmsg_nosec net/socket.c:1044 [inline] >> sock_recvmsg net/socket.c:1066 [inline] >> __sys_recvfrom+0x476/0x860 net/socket.c:2246 >> __do_sys_recvfrom net/socket.c:2264 [inline] >> __se_sys_recvfrom net/socket.c:2260 [inline] >> __x64_sys_recvfrom+0x130/0x200 net/socket.c:2260 >> do_syscall_x64 arch/x86/entry/common.c:51 [inline] >> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82 >> entry_SYSCALL_64_after_hwframe+0x63/0x6b >> >> Uninit was created at: >> slab_post_alloc_hook+0x103/0x9e0 mm/slab.h:768 >> slab_alloc_node mm/slub.c:3478 [inline] >> kmem_cache_alloc_node+0x5f7/0xb50 mm/slub.c:3523 >> kmalloc_reserve+0x13c/0x4a0 net/core/skbuff.c:560 >> __alloc_skb+0x2fd/0x770 net/core/skbuff.c:651 >> alloc_skb include/linux/skbuff.h:1286 [inline] >> tipc_tlv_alloc net/tipc/netlink_compat.c:156 [inline] >> tipc_get_err_tlv+0x90/0x5d0 net/tipc/netlink_compat.c:170 >> tipc_nl_compat_recv+0x1042/0x15d0 net/tipc/netlink_compat.c:1324 >> genl_family_rcv_msg_doit net/netlink/genetlink.c:972 [inline] >> genl_family_rcv_msg net/netlink/genetlink.c:1052 [inline] >> genl_rcv_msg+0x1220/0x12c0 net/netlink/genetlink.c:1067 >> netlink_rcv_skb+0x4a4/0x6a0 net/netlink/af_netlink.c:2545 >> genl_rcv+0x41/0x60 net/netlink/genetlink.c:1076 >> netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline] >> netlink_unicast+0xf4b/0x1230 net/netlink/af_netlink.c:1368 >> netlink_sendmsg+0x1242/0x1420 net/netlink/af_netlink.c:1910 >> sock_sendmsg_nosec net/socket.c:730 [inline] >> __sock_sendmsg net/socket.c:745 [inline] >> ____sys_sendmsg+0x997/0xd60 net/socket.c:2588 >> ___sys_sendmsg+0x271/0x3b0 net/socket.c:2642 >> __sys_sendmsg net/socket.c:2671 [inline] >> __do_sys_sendmsg net/socket.c:2680 [inline] >> __se_sys_sendmsg net/socket.c:2678 [inline] >> __x64_sys_sendmsg+0x2fa/0x4a0 net/socket.c:2678 >> do_syscall_x64 arch/x86/entry/common.c:51 [inline] >> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82 >> entry_SYSCALL_64_after_hwframe+0x63/0x6b >> >> Bytes 34-35 of 36 are uninitialized >> Memory access of size 36 starts at ffff88802d464a00 >> Data copied to user address 00007ff55033c0a0 >> >> CPU: 0 PID: 30322 Comm: syz-executor.0 Not tainted 6.6.0-14500-g1c41041124bd #10 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014 >> ===================================================== >> >> tipc_add_tlv() puts TLV descriptor and value onto `skb`. This size is >> calculated with TLV_SPACE() macro. It adds the size of struct tlv_desc and >> the length of TLV value passed as an argument, and aligns the result to a >> multiple of TLV_ALIGNTO, i.e., a multiple of 4 bytes. >> >> If the size of struct tlv_desc plus the length of TLV value is not aligned, >> the current implementation leaves the remaining bytes uninitialized. This >> is the cause of the above kernel-infoleak issue. >> >> This patch resolves this issue by clearing data up to an aligned size. >> >> Fixes: d0796d1ef63d ("tipc: convert legacy nl bearer dump to nl compat") >> Signed-off-by: Shigeru Yoshida <syoshida@...hat.com> > > Thanks Yoshida-san, > > I agree with both your analysis and that the fix is correct. > I also agree that the problem was introduced by the cited commit. > > I did wonder if there would be an advantage to only zeroing the > otherwise uninitialised portion of tlv, but I guess that the complexity > isn't worth any gain: all of TLV likely fits into a single cacheline > anyway. > > Reviewed-by: Simon Horman <horms@...nel.org> Hi Simon, Thank you so much for always reviewing my work :) Shigeru > >> --- >> net/tipc/netlink_compat.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c >> index 5bc076f2fa74..c763008a8adb 100644 >> --- a/net/tipc/netlink_compat.c >> +++ b/net/tipc/netlink_compat.c >> @@ -102,6 +102,7 @@ static int tipc_add_tlv(struct sk_buff *skb, u16 type, void *data, u16 len) >> return -EMSGSIZE; >> >> skb_put(skb, TLV_SPACE(len)); >> + memset(tlv, 0, TLV_SPACE(len)); >> tlv->tlv_type = htons(type); >> tlv->tlv_len = htons(TLV_LENGTH(len)); >> if (len && data) >> -- >> 2.41.0 >> >> >
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