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SubjectRe: [PATCH] arm64: defconfig: update and enable CONFIG_RANDOMIZE_BASE
On Mon, Jun 24, 2019 at 12:06:18PM +0200, Ard Biesheuvel wrote:
> On Mon, 24 Jun 2019 at 11:57, Will Deacon <will@kernel.org> wrote:
> > Thanks for having a look. It could be that we've fixed the issue Catalin was
> > running into in the past -- he was going to see if the problem persists with
> > mainline, since it was frequent enough that it was causing us to ignore the
> > results from our testing infrastructure when RANDOMIZE_BASE=y.
>
> I had no idea this was the case. I can look into it if we are still
> seeing failures.

I've seen the panic below with 5.2-rc1, defconfig + RANDOMIZE_BASE=y in
a guest on TX2. It takes a few tries to trigger just with kaslr,
enabling lots of other DEBUG_* options makes the failures more
deterministic. I can't really say it's kaslr's fault here, only that I
used to consistently get it in this configuration. For some reason, I
can no longer reproduce it on arm64 for-next/core (or maybe it just
takes more tries and my script doesn't catch this).

The fault is in the ip_tables module, the __this_cpu_read in
xt_write_recseq_begin() inlined in ipt_do_table(). The disassembled
sequence in my build:

0000000000000188 <ipt_do_table>:
...
258: d538d080 mrs x0, tpidr_el1
25c: aa1303f9 mov x25, x19
260: b8606b34 ldr w20, [x25, x0]

# modprobe iptable_filter
[ 45.618896] Unable to handle kernel paging request at virtual address ffffeda0ffbe1388
[ 45.620545] Mem abort info:
[ 45.621035] ESR = 0x96000005
[ 45.621559] Exception class = DABT (current EL), IL = 32 bits
[ 45.622527] SET = 0, FnV = 0
[ 45.623032] EA = 0, S1PTW = 0
[ 45.623684] Data abort info:
[ 45.624192] ISV = 0, ISS = 0x00000005
[ 45.624849] CM = 0, WnR = 0
[ 45.625361] swapper pgtable: 4k pages, 48-bit VAs, pgdp = 0000000026cb760e
[ 45.626537] [ffffeda0ffbe1388] pgd=00000000bfffa003, pud=0000000000000000
[ 45.627864] Internal error: Oops: 96000005 [#1] PREEMPT SMP
[ 45.628844] Modules linked in: iptable_filter cfg80211 rfkill 8021q garp crct10dif_ce stp mrp llc ip_tables x_tables ipv6
[ 45.630700] Process kworker/u8:5 (pid: 173, stack limit = 0x0000000047fc7e17)
[ 45.632056] CPU: 3 PID: 173 Comm: kworker/u8:5 Not tainted 5.2.0-rc1 #1
[ 45.633377] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
[ 45.634752] Workqueue: rpciod rpc_async_schedule
[ 45.635684] pstate: 80400005 (Nzcv daif +PAN -UAO)
[ 45.636674] pc : ipt_do_table+0xd8/0x4b8 [ip_tables]
[ 45.637686] lr : ipt_do_table+0xc4/0x4b8 [ip_tables]
[ 45.638685] sp : ffff000010aa35a0
[ 45.639358] x29: ffff000010aa35a0 x28: ffffeda1f7eb0ce8
[ 45.640424] x27: ffffeda1e69f1380 x26: ffff5d2c2314a288
[ 45.641493] x25: ffff5d2c0cfbf388 x24: ffffeda1fb5a9000
[ 45.642556] x23: ffff5d2c2314a220 x22: 0000000000000003
[ 45.643636] x21: ffffeda1f79c15d8 x20: ffffeda1e69f1780
[ 45.644727] x19: ffff5d2c0cfbf388 x18: 0000000000000000
[ 45.645814] x17: 0000000000000000 x16: ffff5d2d0bc16d78
[ 45.646908] x15: 0000000000000000 x14: 0900000017ea6502
[ 45.647994] x13: 014a023b4751727f x12: 0000000000002238
[ 45.649060] x11: ffff5d2d0e0de000 x10: 0000000000004000
[ 45.650117] x9 : 000000000000000e x8 : ffffeda1fb5a9000
[ 45.651178] x7 : ffffeda1f7eb0c00 x6 : 00000000000000e8
[ 45.652263] x5 : 0000000000000080 x4 : 00009074f2c22000
[ 45.653286] x3 : 0000000000000200 x2 : ffffeda1fc41c440
[ 45.654314] x1 : ffff5d2c2314a000 x0 : 00009074f2c22000
[ 45.655382] Call trace:
[ 45.655896] ipt_do_table+0xd8/0x4b8 [ip_tables]
[ 45.656825] iptable_filter_hook+0x1c/0x28 [iptable_filter]
[ 45.657938] nf_hook_slow+0x44/0xe8
[ 45.658647] __ip_local_out+0x150/0x250
[ 45.659421] ip_local_out+0x20/0x80
[ 45.660142] __ip_queue_xmit+0x1b0/0x540
[ 45.660937] ip_queue_xmit+0x10/0x18
[ 45.661661] __tcp_transmit_skb+0x50c/0xad8
[ 45.662494] tcp_write_xmit+0x6cc/0x1010
[ 45.663294] __tcp_push_pending_frames+0x38/0xc0
[ 45.664236] tcp_push+0x150/0x170
[ 45.664912] tcp_sendmsg_locked+0xaa0/0xc40
[ 45.665754] tcp_sendmsg+0x34/0x58
[ 45.666442] inet_sendmsg+0x48/0x210
[ 45.667175] sock_sendmsg+0x18/0x30
[ 45.667889] xs_sendpages+0xfc/0x2d8
[ 45.668610] xs_tcp_send_request+0x9c/0x1b0
[ 45.669454] xprt_transmit+0x100/0x5b8
[ 45.670210] call_transmit+0x8c/0xa0
[ 45.670938] __rpc_execute+0xbc/0x580
[ 45.671687] rpc_async_schedule+0x28/0x48
[ 45.672493] process_one_work+0x244/0x680
[ 45.673306] worker_thread+0x40/0x3f0
[ 45.674053] kthread+0x128/0x130
[ 45.674710] ret_from_fork+0x10/0x18
[ 45.675436] Code: b0f4f3d3 910e2273 d538d080 aa1303f9 (b8606b34)
[ 45.676665] ---[ end trace 9d1f75fe6e41c0d7 ]---
[ 45.677590] Kernel panic - not syncing: Fatal exception in interrupt
[ 45.678851] SMP: stopping secondary CPUs
[ 45.679670] Kernel Offset: 0x5d2cfb600000 from 0xffff000010000000
[ 45.680882] PHYS_OFFSET: 0xffff925ec0000000
[ 45.681727] CPU features: 0x002,23800438
[ 45.682518] Memory Limit: none
[ 45.683143] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---

--
Catalin

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