From: Martynas Pumputis Date: Fri, 23 Nov 2018 16:43:26 +0000 (+0100) Subject: bpf: fix check of allowed specifiers in bpf_trace_printk X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=9209043b29881a7ede5e34610c4feadd29e59e40;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git bpf: fix check of allowed specifiers in bpf_trace_printk [ Upstream commit 1efb6ee3edea57f57f9fb05dba8dcb3f7333f61f ] A format string consisting of "%p" or "%s" followed by an invalid specifier (e.g. "%p%\n" or "%s%") could pass the check which would make format_decode (lib/vsprintf.c) to warn. Fixes: 9c959c863f82 ("tracing: Allow BPF programs to call bpf_trace_printk()") Reported-by: syzbot+1ec5c5ec949c4adaa0c4@syzkaller.appspotmail.com Signed-off-by: Martynas Pumputis Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin --- diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 6350f64d5aa4..f9dd8fd055a6 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -161,11 +161,13 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, i++; } else if (fmt[i] == 'p' || fmt[i] == 's') { mod[fmt_cnt]++; - i++; - if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0) + /* disallow any further format extensions */ + if (fmt[i + 1] != 0 && + !isspace(fmt[i + 1]) && + !ispunct(fmt[i + 1])) return -EINVAL; fmt_cnt++; - if (fmt[i - 1] == 's') { + if (fmt[i] == 's') { if (str_seen) /* allow only one '%s' per fmt string */ return -EINVAL;