From: Zheng Yejian Date: Mon, 14 Nov 2022 10:46:32 +0000 (+0800) Subject: tracing: Fix potential null-pointer-access of entry in list 'tr->err_log' X-Git-Tag: v6.1~92^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=067df9e0ad48a97382ab2179bbe773a13a846028;p=platform%2Fkernel%2Flinux-starfive.git tracing: Fix potential null-pointer-access of entry in list 'tr->err_log' Entries in list 'tr->err_log' will be reused after entry number exceed TRACING_LOG_ERRS_MAX. The cmd string of the to be reused entry will be freed first then allocated a new one. If the allocation failed, then the entry will still be in list 'tr->err_log' but its 'cmd' field is set to be NULL, later access of 'cmd' is risky. Currently above problem can cause the loss of 'cmd' information of first entry in 'tr->err_log'. When execute `cat /sys/kernel/tracing/error_log`, reproduce logs like: [ 37.495100] trace_kprobe: error: Maxactive is not for kprobe(null) ^ [ 38.412517] trace_kprobe: error: Maxactive is not for kprobe Command: p4:myprobe2 do_sys_openat2 ^ Link: https://lore.kernel.org/linux-trace-kernel/20221114104632.3547266-1-zhengyejian1@huawei.com Fixes: 1581a884b7ca ("tracing: Remove size restriction on tracing_log_err cmd strings") Signed-off-by: Zheng Yejian Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) --- diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5bd202d..a7fe0e1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7803,6 +7803,7 @@ static struct tracing_log_err *get_tracing_log_err(struct trace_array *tr, int len) { struct tracing_log_err *err; + char *cmd; if (tr->n_err_log_entries < TRACING_LOG_ERRS_MAX) { err = alloc_tracing_log_err(len); @@ -7811,12 +7812,12 @@ static struct tracing_log_err *get_tracing_log_err(struct trace_array *tr, return err; } - + cmd = kzalloc(len, GFP_KERNEL); + if (!cmd) + return ERR_PTR(-ENOMEM); err = list_first_entry(&tr->err_log, struct tracing_log_err, list); kfree(err->cmd); - err->cmd = kzalloc(len, GFP_KERNEL); - if (!err->cmd) - return ERR_PTR(-ENOMEM); + err->cmd = cmd; list_del(&err->list); return err;