[Bug 265569] [panic] Fatal trap 9: general protection fault while in kernel mode arc_reap

From: <bugzilla-noreply_at_freebsd.org>
Date: Tue, 02 Aug 2022 06:30:09 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=265569

--- Comment #1 from Charlie Stanley <postmaster@willardstanley.com> ---
I was doing some more debugging and the call chain looks sane until the slab
address is computed. The slab pointer seems to be at an odd offset, and when I
dereference it, the data looks like garbage to my limited understanding.

(kgdb) frame 8
#8  zone_release (arg=0xfffffe015a7c8000, bucket=0xfffff80f4784e410,
cnt=<optimized out>) at /usr/src/sys/vm/uma_core.c:4730
4730                    slab_free_item(zone, slab, item);
(kgdb) print zone
$19 = (uma_zone_t) 0xfffffe015a7c8000
(kgdb) print slab
$20 = (uma_slab_t) 0xfffff80e00000158
(kgdb) print *zone
$21 = {uz_flags = 10551296, uz_size = 4096, uz_ctor = 0x0, uz_dtor = 0x0,
uz_smr = 0x0, uz_max_items = 0, uz_bucket_max = 18446744073709551615,
uz_bucket_size = 80, uz_bucket_size_max = 254, uz_sleepers = 0, uz_xdomain =
0xfffffe01d3cb4590, uz_keg = 0xfffff80005f13a80, 
  uz_import = 0xffffffff80f4a370 <zone_import>, uz_release = 0xffffffff80f465e0
<zone_release>, uz_arg = 0xfffffe015a7c8000, uz_init = 0x0, uz_fini = 0x0,
uz_items = 0, uz_sleeps = 0, uz_link = {le_next = 0x0, le_prev =
0xfffff80005f13a90}, uz_allocs = 0xfffffe01d3cb45a8, 
  uz_frees = 0xfffffe01d3cb45a0, uz_fails = 0xfffffe01d3cb4598, uz_name =
0xfffff80005f0a180 "abd_chunk", uz_ctlname = 0xfffff80005f18de0 "abd_chunk",
uz_namecnt = 0, uz_bucket_size_min = 2, uz_reclaimers = 1, uz_oid =
0xfffff80005f07b80, uz_warning = 0x0, uz_ratecheck = {
    tv_sec = 0, tv_usec = 0}, uz_maxaction = {ta_link = {stqe_next = 0x0},
ta_pending = 0, ta_priority = 0 '\000', ta_flags = 0 '\000', ta_func = 0x0,
ta_context = 0x0}, uz_cross_lock = {lock_object = {lo_name = 0xffffffff812a0598
"UMA Cross", lo_flags = 16973824, 
      lo_data = 0, lo_witness = 0x0}, mtx_lock = 0}, uz_cpu =
0xfffffe015a7c8180}
(kgdb) print *slab
$22 = {us_link = {le_next = 0xda39576285989539, le_prev = 0x732ca6f15f8ff3dc},
us_freecount = 4147, us_flags = 27 '\033', us_domain = 120 'x', us_free =
{__bits = 0xfffff80e00000170}}

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