From 4ca530852346be239b7c19e7bec5d2b78855bebe Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 16 Mar 2009 19:20:15 -0400 Subject: [PATCH] tracing: protect reader of cmdline output Impact: fix to one cause of incorrect comm outputs in trace The spinlock only protected the creation of a comm <=> pid pair. But it was possible that a reader could look up a pid, and get the wrong comm because it had no locking. This also required changing trace_find_cmdline to copy the comm cache and not just send back a pointer to it. Signed-off-by: Steven Rostedt --- kernel/trace/blktrace.c | 23 ++++++++++++++++++----- kernel/trace/trace.c | 20 ++++++++++++-------- kernel/trace/trace.h | 2 +- kernel/trace/trace_functions_graph.c | 12 ++++++------ kernel/trace/trace_output.c | 18 ++++++++++++------ 5 files changed, 49 insertions(+), 26 deletions(-) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 1f32e4edf49..b171778e386 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1027,7 +1027,9 @@ static int blk_log_action_seq(struct trace_seq *s, const struct blk_io_trace *t, static int blk_log_generic(struct trace_seq *s, const struct trace_entry *ent) { - const char *cmd = trace_find_cmdline(ent->pid); + char cmd[TASK_COMM_LEN]; + + trace_find_cmdline(ent->pid, cmd); if (t_sec(ent)) return trace_seq_printf(s, "%llu + %u [%s]\n", @@ -1057,19 +1059,30 @@ static int blk_log_remap(struct trace_seq *s, const struct trace_entry *ent) static int blk_log_plug(struct trace_seq *s, const struct trace_entry *ent) { - return trace_seq_printf(s, "[%s]\n", trace_find_cmdline(ent->pid)); + char cmd[TASK_COMM_LEN]; + + trace_find_cmdline(ent->pid, cmd); + + return trace_seq_printf(s, "[%s]\n", cmd); } static int blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent) { - return trace_seq_printf(s, "[%s] %llu\n", trace_find_cmdline(ent->pid), - get_pdu_int(ent)); + char cmd[TASK_COMM_LEN]; + + trace_find_cmdline(ent->pid, cmd); + + return trace_seq_printf(s, "[%s] %llu\n", cmd, get_pdu_int(ent)); } static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent) { + char cmd[TASK_COMM_LEN]; + + trace_find_cmdline(ent->pid, cmd); + return trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent), - get_pdu_int(ent), trace_find_cmdline(ent->pid)); + get_pdu_int(ent), cmd); } /* diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index efe3202c020..2796bd2b17e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -770,25 +770,29 @@ static void trace_save_cmdline(struct task_struct *tsk) __raw_spin_unlock(&trace_cmdline_lock); } -char *trace_find_cmdline(int pid) +void trace_find_cmdline(int pid, char comm[]) { - char *cmdline = "<...>"; unsigned map; - if (!pid) - return ""; + if (!pid) { + strcpy(comm, ""); + return; + } - if (pid > PID_MAX_DEFAULT) - goto out; + if (pid > PID_MAX_DEFAULT) { + strcpy(comm, "<...>"); + return; + } + __raw_spin_lock(&trace_cmdline_lock); map = map_pid_to_cmdline[pid]; if (map >= SAVED_CMDLINES) goto out; - cmdline = saved_cmdlines[map]; + strcpy(comm, saved_cmdlines[map]); out: - return cmdline; + __raw_spin_unlock(&trace_cmdline_lock); } void tracing_record_cmdline(struct task_struct *tsk) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 56ce34d90b0..b0ecad8ecc3 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -547,7 +547,7 @@ struct tracer_switch_ops { }; #endif /* CONFIG_CONTEXT_SWITCH_TRACER */ -extern char *trace_find_cmdline(int pid); +extern void trace_find_cmdline(int pid, char comm[]); #ifdef CONFIG_DYNAMIC_FTRACE extern unsigned long ftrace_update_tot_cnt; diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c index 4c388607ed6..6004ccac2dd 100644 --- a/kernel/trace/trace_functions_graph.c +++ b/kernel/trace/trace_functions_graph.c @@ -190,15 +190,15 @@ print_graph_cpu(struct trace_seq *s, int cpu) static enum print_line_t print_graph_proc(struct trace_seq *s, pid_t pid) { - int i; - int ret; - int len; - char comm[8]; - int spaces = 0; + char comm[TASK_COMM_LEN]; /* sign + log10(MAX_INT) + '\0' */ char pid_str[11]; + int spaces = 0; + int ret; + int len; + int i; - strncpy(comm, trace_find_cmdline(pid), 7); + trace_find_cmdline(pid, comm); comm[7] = '\0'; sprintf(pid_str, "%d", pid); diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index ea9d3b410c7..6a4c9dea191 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -309,9 +309,9 @@ static int lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu) { int hardirq, softirq; - char *comm; + char comm[TASK_COMM_LEN]; - comm = trace_find_cmdline(entry->pid); + trace_find_cmdline(entry->pid, comm); hardirq = entry->flags & TRACE_FLAG_HARDIRQ; softirq = entry->flags & TRACE_FLAG_SOFTIRQ; @@ -346,10 +346,12 @@ int trace_print_context(struct trace_iterator *iter) { struct trace_seq *s = &iter->seq; struct trace_entry *entry = iter->ent; - char *comm = trace_find_cmdline(entry->pid); unsigned long long t = ns2usecs(iter->ts); unsigned long usec_rem = do_div(t, USEC_PER_SEC); unsigned long secs = (unsigned long)t; + char comm[TASK_COMM_LEN]; + + trace_find_cmdline(entry->pid, comm); return trace_seq_printf(s, "%16s-%-5d [%03d] %5lu.%06lu: ", comm, entry->pid, iter->cpu, secs, usec_rem); @@ -372,7 +374,10 @@ int trace_print_lat_context(struct trace_iterator *iter) rel_usecs = ns2usecs(next_ts - iter->ts); if (verbose) { - char *comm = trace_find_cmdline(entry->pid); + char comm[TASK_COMM_LEN]; + + trace_find_cmdline(entry->pid, comm); + ret = trace_seq_printf(s, "%16s %5d %3d %d %08x %08lx [%08lx]" " %ld.%03ldms (+%ld.%03ldms): ", comm, entry->pid, iter->cpu, entry->flags, @@ -577,14 +582,15 @@ static enum print_line_t trace_ctxwake_print(struct trace_iterator *iter, char *delim) { struct ctx_switch_entry *field; - char *comm; + char comm[TASK_COMM_LEN]; int S, T; + trace_assign_type(field, iter->ent); T = task_state_char(field->next_state); S = task_state_char(field->prev_state); - comm = trace_find_cmdline(field->next_pid); + trace_find_cmdline(field->next_pid, comm); if (!trace_seq_printf(&iter->seq, " %5d:%3d:%c %s [%03d] %5d:%3d:%c %s\n", field->prev_pid, -- 2.41.1