Hi all, KMSAN reports a use of uninitialized value on the following program:
========================== // autogenerated by syzkaller (http://github.com/google/syzkaller) #include <string.h> #include <sys/types.h> #include <sys/socket.h> int main() { int sock = socket(PF_KEY, SOCK_RAW, 2); char buf[24]; memset(buf, 0, 24); buf[0] = 2; buf[1] = 4; buf[4] = 3; buf[16] = 1; buf[18] = 0x17; // SADB_X_EXT_NAT_T_OA struct msghdr hdr; memset(&hdr, 0, sizeof(struct msghdr)); struct iovec iov; hdr.msg_iov = &iov; hdr.msg_iovlen = 1; iov.iov_base = buf; iov.iov_len = 0x18; sendmsg(sock, &hdr, 0); } ========================== the report is below: ================================================================== BUG: KMSAN: use of uninitialized memory in pfkey_sendmsg+0x11ad/0x1900 CPU: 0 PID: 2946 Comm: probe Not tainted 4.13.0+ #3626 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: show_stack+0x12f/0x180 arch/x86/kernel/dumpstack.c:177 __dump_stack lib/dump_stack.c:16 dump_stack+0x185/0x1d0 lib/dump_stack.c:52 kmsan_report+0x137/0x1c0 mm/kmsan/kmsan.c:1066 __msan_warning_32+0x69/0xb0 mm/kmsan/kmsan_instr.c:676 verify_address_len net/key/af_key.c:404 parse_exthdrs net/key/af_key.c:532 pfkey_process net/key/af_key.c:2811 pfkey_sendmsg+0x11ad/0x1900 net/key/af_key.c:3654 sock_sendmsg_nosec net/socket.c:633 sock_sendmsg net/socket.c:643 ___sys_sendmsg+0xed5/0x1330 net/socket.c:2035 __sys_sendmsg net/socket.c:2069 SYSC_sendmsg+0x2a6/0x3d0 net/socket.c:2080 SyS_sendmsg+0x54/0x80 net/socket.c:2076 do_syscall_64+0x2f4/0x420 arch/x86/entry/common.c:284 entry_SYSCALL64_slow_path+0x25/0x25 arch/x86/entry/entry_64.S:245 RIP: 0033:0x401140 RSP: 002b:00007ffe52abc9e8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000004002b0 RCX: 0000000000401140 RDX: 0000000000000000 RSI: 00007ffe52abca10 RDI: 0000000000000003 RBP: 00007ffe52abca80 R08: 0000000000000002 R09: 0000000000000004 R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000 R13: 00000000004063e0 R14: 0000000000406470 R15: 0000000000000000 origin: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:63 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:339 kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:346 slab_post_alloc_hook mm/slab.h:442 slab_alloc_node mm/slub.c:2724 __kmalloc_node_track_caller+0xa46/0x1230 mm/slub.c:4335 __kmalloc_reserve net/core/skbuff.c:139 __alloc_skb+0x2c6/0x9f0 net/core/skbuff.c:232 alloc_skb ./include/linux/skbuff.h:904 pfkey_sendmsg+0x201/0x1900 net/key/af_key.c:3641 sock_sendmsg_nosec net/socket.c:633 sock_sendmsg net/socket.c:643 ___sys_sendmsg+0xed5/0x1330 net/socket.c:2035 __sys_sendmsg net/socket.c:2069 SYSC_sendmsg+0x2a6/0x3d0 net/socket.c:2080 SyS_sendmsg+0x54/0x80 net/socket.c:2076 do_syscall_64+0x2f4/0x420 arch/x86/entry/common.c:284 return_from_SYSCALL_64+0x0/0x6a arch/x86/entry/entry_64.S:245 ================================================================== Apparently pfkey_sendmsg reads skb past the end of the buffer copied from the userspace. Could someone please take a look? Thanks, -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
