Max Reitz <mre...@redhat.com> writes: > On 10.09.19 15:36, Sergio Lopez wrote: >> block_job_remove_all_bdrv() iterates through job->nodes, calling >> bdrv_root_unref_child() for each entry. The call to the latter may >> reach child_job_[can_]set_aio_ctx(), which will also attempt to >> traverse job->nodes, potentially finding entries that where freed >> on previous iterations. >> >> To avoid this situation, update job->nodes head on each iteration to >> ensure that already freed entries are no longer linked to the list. >> >> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1746631 >> Signed-off-by: Sergio Lopez <s...@redhat.com> >> --- >> Changelog >> >> v2: >> - Avoid leaking job->nodes (thanks Max Reitz) >> --- >> blockjob.c | 12 ++++++++++-- >> 1 file changed, 10 insertions(+), 2 deletions(-) >> --- >> diff --git a/blockjob.c b/blockjob.c >> index 6e32d1a0c0..ffda6dd1e4 100644 >> --- a/blockjob.c >> +++ b/blockjob.c >> @@ -187,13 +187,21 @@ static const BdrvChildRole child_job = { >> >> void block_job_remove_all_bdrv(BlockJob *job) >> { >> - GSList *l; >> + GSList *l, *orig_nodes; >> + >> + orig_nodes = job->nodes; >> for (l = job->nodes; l; l = l->next) { >> BdrvChild *c = l->data; >> bdrv_op_unblock_all(c->bs, job->blocker); >> bdrv_root_unref_child(c); >> + /* >> + * The call above may reach child_job_[can_]set_aio_ctx(), which >> will >> + * also traverse job->nodes, so update the head here to make sure it >> + * doesn't attempt to process an already freed BdrvChild. >> + */ >> + job->nodes = l->next; >> } >> - g_slist_free(job->nodes); >> + g_slist_free(orig_nodes); >> job->nodes = NULL; > > Hm, this assignment is now a no-op. > > I think I’d just rewrite the whole function in the following fashion: > > orig_nodes = job->nodes; > while (job->nodes) { > BdrvChild *c = job->nodes->data; > [...] > job->nodes = job->nodes->next; > } > g_slist_free(orig_nodes); > > What do you think? >
As this is the first time I was touching this code, I was trying to keep the changes minimal, but I definitely prefer to rewrite the function as you suggest. Should I send a v3, or do you want to send a patch yourself? I don't really mind either, just want to get this fixed ASAP :-) Thanks Max, Sergio.
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