diff options
| author | Martynas Pumputis <m@lambda.lt> | 2018-11-23 17:43:26 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-11-23 21:54:14 +0100 |
| commit | 1efb6ee3edea57f57f9fb05dba8dcb3f7333f61f (patch) | |
| tree | cf6126f29233e979c5cf92c259ad59c315b6318e /kernel | |
| parent | 813961de3ee6474dd5703e883471fd941d6c8f69 (diff) | |
bpf: fix check of allowed specifiers in bpf_trace_printk
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 <m@lambda.lt>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 08fcfe440c63..9864a35c8bb5 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -196,11 +196,13 @@ 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; |