10.0-RC1, armv6: "pfctl -s state" crashes on BeagleBone Black due to unaligned access

[Ermal Luçi]

On Thu, Jan 9, 2014 at 11:42 AM, Gleb Smirnoff <glebius at freebsd.org> wrote:

>   Guy,
>
> On Sat, Jan 04, 2014 at 03:06:02PM +0200, Guy Yur wrote:
> G> I am running 10.0-RC1 arm.armv6 on the BeagleBone Black.
> G> The "pfctl -s state" command is crashing when trying to print the
> G> second entry.
> G>
> G> struct pfsync_state has a size that is not divisiable by 4 or 8 leading
> to the
> G> second entry in the returned state array not being aligned and pfctl
> G> core dumps on Bus error when trying to access a uint32_t field.
> G>
> G> (gdb) bt
> G> #0  print_host (addr=0x2085a11a, port=7660, af=2 '\002', opts=1024) at
> G> /usr/src/sbin/pfctl/pf_print_state.c:178
> G> #1  0x00021c4c in print_state (s=0x2085a0f2, opts=1024) at
> G> /usr/src/sbin/pfctl/pf_print_state.c:236
> G> #2  0x0000c664 in pfctl_show_states (dev=<value optimized out>,
> G> iface=0x0, opts=1024) at /usr/src/sbin/pfctl/pfctl.c:1095
> G>
> G> sizeof(struct pfsync_state_key) is 36
> G> sizeof(struct pfsync_state_peer) is 32
> G> sizeof(struct pf_addr) is 16
> G> sizeof(struct pfsync_state) is 242
> G>
> G> Removing the __spare[2] field will allow the struct to be aligned on 8
> bytes
> G> for the u_int64_t id field and also cover the uint32_t fields alignment
> G> but this will break KBI.
> G>
> G> I am currently using an inefficient workaround in pfctl_show_states
> G> that memcpy each entry to a struct pfsync_state on the stack
> G> ensuring each call to print_state receives an aligned struct.
> G>
> G> 10.0-RC1 World and kernel were compiled in a VirtualBox VM running
> G> 9.2-RELEASE-p2 i386.
> G> clang and ARM_EABI used as the default make options.
>
> For pf we are ready to break KBI. It uses same structs for internal kernel
> representation and for ioctl() API and this is actually a bug. Until it is
> properly fixed, we are doomed to break KBI always.
>
> Unfortunately, pfsync_state is not only a KBI but also a wire protocol for
> pfsync(4). We can't break this, since that would make different FreeBSD
> versions not exchanging states properly.
>
> Well, <= 8.x already is incompatible with >= 9.x, thanks yet another
> OpenBSD
> import. But we don't want to introduce another one.
>
> I will try to fix this making new structure for the ioctl. That will mean
> moving slowly towards divorcing internal structures and ioctl ones.
>
> I'd appreciate if you file a PR on that, so that problem won't leave
> forgotten
> in the mailing list. You can even code the bugfix :)
>
> Thanks!
>
>
Well pfsync has a version in its header so its quite possible to support
many of them.



> --
> Totus tuus, Glebius.
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-- 
Ermal