netfilter: nf_log: don't hold nf_log_mutex during user access
commit ce00bf07cc95a57cd20b208e02b3c2604e532ae8 upstream. 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 commit266d07cb1c
("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:266d07cb1c
("netfilter: nf_log: fix sleeping function calle[...]") Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -274,15 +274,18 @@ static int nf_log_proc_dostring(ctl_table *table, int write,
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rcu_assign_pointer(net->nf.nf_loggers[tindex], logger);
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rcu_assign_pointer(net->nf.nf_loggers[tindex], logger);
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mutex_unlock(&nf_log_mutex);
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mutex_unlock(&nf_log_mutex);
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} else {
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} else {
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struct ctl_table tmp = *table;
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tmp.data = buf;
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mutex_lock(&nf_log_mutex);
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mutex_lock(&nf_log_mutex);
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logger = rcu_dereference_protected(net->nf.nf_loggers[tindex],
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logger = rcu_dereference_protected(net->nf.nf_loggers[tindex],
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lockdep_is_held(&nf_log_mutex));
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lockdep_is_held(&nf_log_mutex));
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if (!logger)
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if (!logger)
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table->data = "NONE";
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strlcpy(buf, "NONE", sizeof(buf));
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else
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else
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table->data = logger->name;
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strlcpy(buf, logger->name, sizeof(buf));
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r = proc_dostring(table, write, buffer, lenp, ppos);
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mutex_unlock(&nf_log_mutex);
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mutex_unlock(&nf_log_mutex);
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r = proc_dostring(&tmp, write, buffer, lenp, ppos);
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}
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}
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return r;
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return r;
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