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Date: Mon, 7 Feb 2022 09:23:53 -0800 From: Yonghong Song <yhs@...com> To: Stanislav Fomichev <sdf@...gle.com>, <netdev@...r.kernel.org>, <bpf@...r.kernel.org> CC: <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>, Lorenzo Bianconi <lorenzo@...nel.org>, syzbot <syzkaller@...glegroups.com> Subject: Re: [PATCH bpf-next 1/2] bpf: test_run: fix overflow in xdp frags parsing On 2/4/22 3:58 PM, Stanislav Fomichev wrote: > When kattr->test.data_size_in > INT_MAX, signed min_t will assign > negative value to data_len. This negative value then gets passed > over to copy_from_user where it is converted to (big) unsigned. > > Use unsigned min_t to avoid this overflow. > > usercopy: Kernel memory overwrite attempt detected to wrapped address > (offset 0, size 18446612140539162846)! > ------------[ cut here ]------------ > kernel BUG at mm/usercopy.c:102! > invalid opcode: 0000 [#1] SMP KASAN > Modules linked in: > CPU: 0 PID: 3781 Comm: syz-executor226 Not tainted 4.15.0-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:usercopy_abort+0xbd/0xbf mm/usercopy.c:102 > RSP: 0018:ffff8801e9703a38 EFLAGS: 00010286 > RAX: 000000000000006c RBX: ffffffff84fc7040 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: ffffffff816560a2 RDI: ffffed003d2e0739 > RBP: ffff8801e9703a90 R08: 000000000000006c R09: 0000000000000001 > R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84fc73a0 > R13: ffffffff84fc7180 R14: ffffffff84fc7040 R15: ffffffff84fc7040 > FS: 00007f54e0bec300(0000) GS:ffff8801f6600000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020000280 CR3: 00000001e90ea000 CR4: 00000000003426f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > check_bogus_address mm/usercopy.c:155 [inline] > __check_object_size mm/usercopy.c:263 [inline] > __check_object_size.cold+0x8c/0xad mm/usercopy.c:253 > check_object_size include/linux/thread_info.h:112 [inline] > check_copy_size include/linux/thread_info.h:143 [inline] > copy_from_user include/linux/uaccess.h:142 [inline] > bpf_prog_test_run_xdp+0xe57/0x1240 net/bpf/test_run.c:989 > bpf_prog_test_run kernel/bpf/syscall.c:3377 [inline] > __sys_bpf+0xdf2/0x4a50 kernel/bpf/syscall.c:4679 > SYSC_bpf kernel/bpf/syscall.c:4765 [inline] > SyS_bpf+0x26/0x50 kernel/bpf/syscall.c:4763 > do_syscall_64+0x21a/0x3e0 arch/x86/entry/common.c:305 > entry_SYSCALL_64_after_hwframe+0x46/0xbb > > Cc: Lorenzo Bianconi <lorenzo@...nel.org> > Fixes: 1c1949982524 ("bpf: introduce frags support to bpf_prog_test_run_xdp()") > Reported-by: syzbot <syzkaller@...glegroups.com> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com> Acked-by: Yonghong Song <yhs@...com>
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