Commit 19c8d8ac authored Jun 08, 2020 by Andrew Morton Committed by Linus Torvalds Jun 09, 2020

bpf:bpf_seq_printf(): handle potentially unsafe format string better

User the proper helper for kernel or userspace addresses based on
TASK_SIZE instead of the dangerous strncpy_from_unsafe function.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent aec6ce59

kernel/trace/bpf_trace.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -588,15 +588,17 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file , m, char , fmt, u32, fmt_size,
		}

		if (fmt[i] == 's') {
		void *unsafe_ptr;

		/* try our best to copy */
		if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
		err = -E2BIG;
		goto out;
		}

		err = strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt],
		(void *) (long) args[fmt_cnt],
		MAX_SEQ_PRINTF_STR_LEN);
		unsafe_ptr = (void *)(long)args[fmt_cnt];
		err = strncpy_from_kernel_nofault(bufs->buf[memcpy_cnt],
		unsafe_ptr, MAX_SEQ_PRINTF_STR_LEN);
		if (err < 0)
		bufs->buf[memcpy_cnt][0] = '\0';
		params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt];

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