Michal Prívozník <mprivozn@redhat.com> [2018-08-27, 04:03PM +0200]:
On 08/27/2018 03:20 PM, Marc Hartmayer wrote:
If @vm has flagged as "to be removed" virDomainObjListFindByNameLocked returns NULL (although the definition actually exists). Therefore, the possibility exits that "virHashAddEntry" will raise the error "Duplicate key" => virDomainObjListAddObjLocked fails => virDomainObjEndAPI(&vm) is called and this leads to a freeing of @def since @def is already assigned to vm->def. But actually this leads to a double free since the common usage pattern is that the caller of virDomainObjListAdd(Locked) is responsible for freeing @def in case of an error.
Let's fix this by setting vm->def to NULL in case of an error.
Backtrace:
➤ bt #0 virFree (ptrptr=0x7575757575757575) #1 0x000003ffb5b25b3e in virDomainResourceDefFree #2 0x000003ffb5b37c34 in virDomainDefFree #3 0x000003ff9123f734 in qemuDomainDefineXMLFlags #4 0x000003ff9123f7f4 in qemuDomainDefineXML #5 0x000003ffb5cd2c84 in virDomainDefineXML #6 0x000000011745aa82 in remoteDispatchDomainDefineXML ...
Reviewed-by: Bjoern Walk <bwalk@linux.ibm.com> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com> --- src/conf/virdomainobjlist.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/src/conf/virdomainobjlist.c b/src/conf/virdomainobjlist.c index 52171594f34f..805fe9440afe 100644 --- a/src/conf/virdomainobjlist.c +++ b/src/conf/virdomainobjlist.c @@ -329,8 +329,10 @@ virDomainObjListAddLocked(virDomainObjListPtr doms, goto cleanup; vm->def = def;
- if (virDomainObjListAddObjLocked(doms, vm) < 0) + if (virDomainObjListAddObjLocked(doms, vm) < 0) { + vm->def = NULL; goto error; + } } cleanup: return vm;
How about setting vm->def only after virDomainObjListAddObjLocked() succeded?
However, this points to a more sever bug. If a domain is being removed, and some other thread is trying to define it back, I guess the whole operation should succeed. Definitely not fail with some (for user) cryptic message like "double key found in a hash table".
The problem is that:
a) both virDomainObjListFindByUUIDLocked() and virDomainObjListFindByNameLocked() return NULL even if domain exists. They should return the found domain and only the caller should decide if vm->removing is relevant or not.
b) nothing is clearing out the vm->removing flag. The virDomainObjListAddObjLocked() looks like a good candidate to do so.
Michal
Can we still take this fix for the upcoming release and worry about doing it right later?
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