[pve-devel] [PATCH qemu] cherry-pick segfault fix

[Fabian Grünbichler]

this was reported multiple times in our forums[1 with backtraces, 2 & 3
with same log messages], fix is taken from upstream master.

1: https://forum.proxmox.com/threads/pve-7-0-14-1-vm-not-running-live-migration-kills-vm-post-ssd-move-pre-ram-move.99704/
2: https://forum.proxmox.com/threads/proxmox-7-0-14-1-crashes-vm-during-migrate-to-other-host.99678
3: https://forum.proxmox.com/threads/cannot-migrate-between-zfs-and-ceph.99685/#post-430152

Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
---
gave it a quick spin with some NBD migrations, and the patch itselfs
looks very straight-forward..

 ...-NULL-pointer-dereference-in-mirror_.patch | 85 +++++++++++++++++++
 debian/patches/series                         |  1 +
 2 files changed, 86 insertions(+)
 create mode 100644 debian/patches/extra/0007-block-mirror-fix-NULL-pointer-dereference-in-mirror_.patch

diff --git a/debian/patches/extra/0007-block-mirror-fix-NULL-pointer-dereference-in-mirror_.patch b/debian/patches/extra/0007-block-mirror-fix-NULL-pointer-dereference-in-mirror_.patch
new file mode 100644
index 0000000..f108313
--- /dev/null
+++ b/debian/patches/extra/0007-block-mirror-fix-NULL-pointer-dereference-in-mirror_.patch
@@ -0,0 +1,85 @@
+From 14889c02315b196f28b02832362dead64b015b6e Mon Sep 17 00:00:00 2001
+From: Stefano Garzarella <sgarzare at redhat.com>
+Date: Fri, 10 Sep 2021 14:45:33 +0200
+Subject: [PATCH qemu] block/mirror: fix NULL pointer dereference in
+ mirror_wait_on_conflicts()
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+In mirror_iteration() we call mirror_wait_on_conflicts() with
+`self` parameter set to NULL.
+
+Starting from commit d44dae1a7c we dereference `self` pointer in
+mirror_wait_on_conflicts() without checks if it is not NULL.
+
+Backtrace:
+  Program terminated with signal SIGSEGV, Segmentation fault.
+  #0  mirror_wait_on_conflicts (self=0x0, s=<optimized out>, offset=<optimized out>, bytes=<optimized out>)
+      at ../block/mirror.c:172
+  172	                self->waiting_for_op = op;
+  [Current thread is 1 (Thread 0x7f0908931ec0 (LWP 380249))]
+  (gdb) bt
+  #0  mirror_wait_on_conflicts (self=0x0, s=<optimized out>, offset=<optimized out>, bytes=<optimized out>)
+      at ../block/mirror.c:172
+  #1  0x00005610c5d9d631 in mirror_run (job=0x5610c76a2c00, errp=<optimized out>) at ../block/mirror.c:491
+  #2  0x00005610c5d58726 in job_co_entry (opaque=0x5610c76a2c00) at ../job.c:917
+  #3  0x00005610c5f046c6 in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>)
+      at ../util/coroutine-ucontext.c:173
+  #4  0x00007f0909975820 in ?? () at ../sysdeps/unix/sysv/linux/x86_64/__start_context.S:91
+      from /usr/lib64/libc.so.6
+
+Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2001404
+Fixes: d44dae1a7c ("block/mirror: fix active mirror dead-lock in mirror_wait_on_conflicts")
+Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
+Message-Id: <20210910124533.288318-1-sgarzare at redhat.com>
+Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov at virtuozzo.com>
+Signed-off-by: Hanna Reitz <hreitz at redhat.com>
+(cherry picked from commit 66fed30c9cd11854fc878a4eceb507e915d7c9cd)
+Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
+---
+ block/mirror.c | 25 ++++++++++++++++---------
+ 1 file changed, 16 insertions(+), 9 deletions(-)
+
+diff --git a/block/mirror.c b/block/mirror.c
+index 33477ade1b..6a126d18c8 100644
+--- a/block/mirror.c
++++ b/block/mirror.c
+@@ -162,18 +162,25 @@ static void coroutine_fn mirror_wait_on_conflicts(MirrorOp *self,
+             if (ranges_overlap(self_start_chunk, self_nb_chunks,
+                                op_start_chunk, op_nb_chunks))
+             {
+-                /*
+-                 * If the operation is already (indirectly) waiting for us, or
+-                 * will wait for us as soon as it wakes up, then just go on
+-                 * (instead of producing a deadlock in the former case).
+-                 */
+-                if (op->waiting_for_op) {
+-                    continue;
++                if (self) {
++                    /*
++                     * If the operation is already (indirectly) waiting for us,
++                     * or will wait for us as soon as it wakes up, then just go
++                     * on (instead of producing a deadlock in the former case).
++                     */
++                    if (op->waiting_for_op) {
++                        continue;
++                    }
++
++                    self->waiting_for_op = op;
+                 }
+ 
+-                self->waiting_for_op = op;
+                 qemu_co_queue_wait(&op->waiting_requests, NULL);
+-                self->waiting_for_op = NULL;
++
++                if (self) {
++                    self->waiting_for_op = NULL;
++                }
++
+                 break;
+             }
+         }
+-- 
+2.30.2
+
diff --git a/debian/patches/series b/debian/patches/series
index c1eecec..92bcf10 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -4,6 +4,7 @@ extra/0003-monitor-hmp-add-support-for-flag-argument-with-value.patch
 extra/0004-monitor-refactor-set-expire_password-and-allow-VNC-d.patch
 extra/0005-monitor-hmp-correctly-invert-password-argument-detec.patch
 extra/0006-qxl-fix-pre-save-logic.patch
+extra/0007-block-mirror-fix-NULL-pointer-dereference-in-mirror_.patch
 bitmap-mirror/0001-drive-mirror-add-support-for-sync-bitmap-mode-never.patch
 bitmap-mirror/0002-drive-mirror-add-support-for-conditional-and-always-.patch
 bitmap-mirror/0003-mirror-add-check-for-bitmap-mode-without-bitmap.patch
-- 
2.30.2