[Qemu-devel] [Bug 1840865] [NEW] qemu crashes when doing iotest on virtio-9p filesystem

[fangying]

Public bug reported:

Qemu crashes when doing avocado-vt test on virtio-9p filesystem.
This bug can be reproduced running 
https://github.com/autotest/tp-qemu/blob/master/qemu/tests/9p.py.
The crash stack goes like:

Program terminated with signal SIGSEGV, Segmentation fault.
#0  v9fs_mark_fids_unreclaim (pdu=pdu@entry=0xaaab00046868, 
path=path@entry=0xffff851e2fa8)
    at hw/9pfs/9p.c:505
#1  0x0000aaaae3585acc in v9fs_unlinkat (opaque=0xaaab00046868) at 
hw/9pfs/9p.c:2590
#2  0x0000aaaae3811c10 in coroutine_trampoline (i0=<optimized out>, 
i1=<optimized out>)
    at util/coroutine-ucontext.c:116
#3  0x0000ffffa13ddb20 in ?? () from /lib64/libc.so.6
Backtrace stopped: not enough registers or memory available to unwind further

A segment fault is triggered at hw/9pfs/9p.c line 505

    for (fidp = s->fid_list; fidp; fidp = fidp->next) {
        if (fidp->path.size != path->size) {     # fidp is invalid 
            continue;
        }

(gdb) p path
$10 = (V9fsPath *) 0xffff851e2fa8
(gdb) p *path
$11 = {size = 21, data = 0xaaaafed6f420 "./9p_test/p2a1/d0/f1"}
(gdb) p *fidp
Cannot access memory at address 0x101010101010101
(gdb) p *pdu
$12 = {size = 19, tag = 54, id = 76 'L', cancelled = 0 '\000', complete = 
{entries = {
      sqh_first = 0x0, sqh_last = 0xaaab00046870}}, s = 0xaaab000454b8, next = {
    le_next = 0xaaab000467c0, le_prev = 0xaaab00046f88}, idx = 88}
(gdb) 

Address Sanitizer shows error and saying that there is a heap-use-after-
free on *fidp*.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1840865

Title:
  qemu crashes when doing iotest on  virtio-9p filesystem

Status in QEMU:
  New

Bug description:
  Qemu crashes when doing avocado-vt test on virtio-9p filesystem.
  This bug can be reproduced running 
https://github.com/autotest/tp-qemu/blob/master/qemu/tests/9p.py.
  The crash stack goes like:

  Program terminated with signal SIGSEGV, Segmentation fault.
  #0  v9fs_mark_fids_unreclaim (pdu=pdu@entry=0xaaab00046868, 
path=path@entry=0xffff851e2fa8)
      at hw/9pfs/9p.c:505
  #1  0x0000aaaae3585acc in v9fs_unlinkat (opaque=0xaaab00046868) at 
hw/9pfs/9p.c:2590
  #2  0x0000aaaae3811c10 in coroutine_trampoline (i0=<optimized out>, 
i1=<optimized out>)
      at util/coroutine-ucontext.c:116
  #3  0x0000ffffa13ddb20 in ?? () from /lib64/libc.so.6
  Backtrace stopped: not enough registers or memory available to unwind further

  A segment fault is triggered at hw/9pfs/9p.c line 505

      for (fidp = s->fid_list; fidp; fidp = fidp->next) {
          if (fidp->path.size != path->size) {     # fidp is invalid 
              continue;
          }

  (gdb) p path
  $10 = (V9fsPath *) 0xffff851e2fa8
  (gdb) p *path
  $11 = {size = 21, data = 0xaaaafed6f420 "./9p_test/p2a1/d0/f1"}
  (gdb) p *fidp
  Cannot access memory at address 0x101010101010101
  (gdb) p *pdu
  $12 = {size = 19, tag = 54, id = 76 'L', cancelled = 0 '\000', complete = 
{entries = {
        sqh_first = 0x0, sqh_last = 0xaaab00046870}}, s = 0xaaab000454b8, next 
= {
      le_next = 0xaaab000467c0, le_prev = 0xaaab00046f88}, idx = 88}
  (gdb) 

  Address Sanitizer shows error and saying that there is a heap-use-
  after-free on *fidp*.

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