| Message ID | 20180625152200.200145-1-jannh@google.com |
|---|---|
| State | Awaiting Upstream, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] netfilter: nf_log: don't hold nf_log_mutex during user access | expand |
On Mon, Jun 25, 2018 at 05:22:00PM +0200, Jann Horn wrote: > The old code would indefinitely block other users of nf_log_mutex if > a userspace access in proc_dostring() blocked e.g. due to a userfaultfd > region. Fix it by moving proc_dostring() out of the locked region. > > This is a followup to commit 266d07cb1c9a ("netfilter: nf_log: fix > sleeping function called from invalid context"), which changed this code > from using rcu_read_lock() to taking nf_log_mutex. Applied.
diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c index 426457047578..95b92954b896 100644 --- a/net/netfilter/nf_log.c +++ b/net/netfilter/nf_log.c @@ -442,14 +442,17 @@ static int nf_log_proc_dostring(struct ctl_table *table, int write, rcu_assign_pointer(net->nf.nf_loggers[tindex], logger); mutex_unlock(&nf_log_mutex); } else { + struct ctl_table tmp = *table; + + tmp.data = buf; mutex_lock(&nf_log_mutex); logger = nft_log_dereference(net->nf.nf_loggers[tindex]); if (!logger) - table->data = "NONE"; + strlcpy(buf, "NONE", sizeof(buf)); else - table->data = logger->name; - r = proc_dostring(table, write, buffer, lenp, ppos); + strlcpy(buf, logger->name, sizeof(buf)); mutex_unlock(&nf_log_mutex); + r = proc_dostring(&tmp, write, buffer, lenp, ppos); } return r;
The old code would indefinitely block other users of nf_log_mutex if a userspace access in proc_dostring() blocked e.g. due to a userfaultfd region. Fix it by moving proc_dostring() out of the locked region. This is a followup to commit 266d07cb1c9a ("netfilter: nf_log: fix sleeping function called from invalid context"), which changed this code from using rcu_read_lock() to taking nf_log_mutex. Fixes: 266d07cb1c9a ("netfilter: nf_log: fix sleeping function calle[...]") Signed-off-by: Jann Horn <jannh@google.com> --- net/netfilter/nf_log.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)