Messages in this thread | | | Subject | Re: [PATCH] bpf: check size before calling kvmalloc | From | Daniel Borkmann <> | Date | Fri, 17 Dec 2021 23:45:53 +0100 |
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On 12/17/21 7:48 PM, George Kennedy wrote: > ZERO_SIZE_PTR ((void *)16) is returned by kvmalloc() instead of NULL > if size is zero. Currently, return values from kvmalloc() are only > checked for NULL. Before calling kvmalloc() check for size of zero > and return error if size is zero to avoid the following crash. > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > PGD 1030bd067 P4D 1030bd067 PUD 103497067 PMD 0 > Oops: 0010 [#1] PREEMPT SMP KASAN NOPTI > CPU: 1 PID: 15094 Comm: syz-executor344 Not tainted 5.16.0-rc1-syzk #1 > Hardware name: Red Hat KVM, BIOS > RIP: 0010:0x0 > Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. > RSP: 0018:ffff888017627b78 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: ffff8880215d0780 RCX: ffffffff81b63c60 > RDX: 0000000000000010 RSI: 0000000000000000 RDI: ffff8881035db400 > RBP: ffff888017627f08 R08: ffffed1003697209 R09: ffffed1003697209 > R10: ffff88801b4b9043 R11: ffffed1003697208 R12: ffffffff8f15d580 > R13: 1ffff11002ec4f77 R14: ffff8881035db400 R15: 0000000000000000 > FS: 00007f62bca78740(0000) GS:ffff888107880000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffffffffffffffd6 CR3: 000000002282a000 CR4: 00000000000006e0 > Call Trace: > <TASK> > map_get_next_key kernel/bpf/syscall.c:1279 [inline] > __sys_bpf+0x384d/0x5b30 kernel/bpf/syscall.c:4612 > __do_sys_bpf kernel/bpf/syscall.c:4722 [inline] > __se_sys_bpf kernel/bpf/syscall.c:4720 [inline] > __x64_sys_bpf+0x7a/0xc0 kernel/bpf/syscall.c:4720 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Reported-by: syzkaller <syzkaller@googlegroups.com> > Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Could you provide some more details, e.g. which map type is this where we have to assume zero-sized keys everywhere?
(Or link to syzkaller report could also work alternatively if public.)
Thanks, Daniel
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