Re: [libvirt] [PATCH] conf: utility function to update entry in def->nets array

A virDomainNetDef object in a domain's nets array might contain a virDomainHostdevDef, and when this is the case, the domain's hostdevs array will also have a pointer to this embedded hostdev (this is done so that internal functions that need to perform some operation on all hostdevs won't leave out the type='hostdev' network interfaces). When a network device was updated with virDomainUpdateDeviceFlags(), we were replacing the entry in the nets array (and free'ing the original) but forgetting about the pointer in the hostdevs array (which would then point to the now-free'd hostdev contained in the old net object.) This often resulted in a libvirtd crash. The solution is to add a function, virDomainNetUpdate(), called by qemuDomainUpdateDeviceConfig(), that updates the hostdevs array appropriately along with the nets array. Resolves: https://bugzilla.redhat.com/1558934 Signed-off-by: Laine Stump <laine(a)redhat.com&gt; --- (I actually think that it was a bad idea to have this "reach over" pointer in the hostdevs array (I can say that, since it was my idea :-), and want to eliminate it in favor of using an iterator function for all operations that need to do something to all hostdevs, but this bug exists on old, maintained branches, and I wouldn't want to require backporting anything that disruptive to a stable branch.) Also, I was unable to reproduce the crashes described in the bug report using current upstream code, but could witness (by adding a breakpoint in gdb) the stale pointer when running without this patch, and the correct pointer when running with the patch)

src/conf/domain_conf.c | 41 ++++++++++++++++++++++++++++++++++++++++ src/conf/domain_conf.h | 1 + src/libvirt_private.syms | 1 + src/qemu/qemu_driver.c | 6 ++++-- 4 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 0753904472..5f63c4f51e 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -8786,8 +8786,10 @@ qemuDomainUpdateDeviceConfig(virDomainDefPtr vmdef, false) < 0) return -1; - virDomainNetDefFree(vmdef->nets[pos]); - vmdef->nets[pos] = net; + if (virDomainNetUpdate(vmdef, pos, net)) + return -1; + + virDomainNetDefFree(oldDev.data.net); dev->data.net = NULL; break;