[PATCH] seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_cstr()
STALE1070d
From: Kees Cook <hidden>
Date: 2023-10-26 17:07:39
Also in:
linux-hardening, lkml
Subsystem:
library code, the rest, tracing · Maintainers:
Andrew Morton, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Solve two ergonomic issues with struct seq_buf: 1) Too much boilerplate is required to initialize: struct seq_buf s; char buf[32]; seq_buf_init(s, buf, sizeof(buf)); Instead, we can build this directly on the stack. Provide DECLARE_SEQ_BUF() macro to do this: DECLARE_SEQ_BUF(s, 32); 2) %NUL termination is fragile and requires 2 steps to get a valid C String (and is a layering violation exposing the "internals" of seq_buf): seq_buf_terminate(s); do_something(s->buffer); Instead, we can just return s->buffer direction after terminating it in refactored seq_buf_terminate(), now known as seq_buf_cstr(): do_soemthing(seq_buf_cstr(s)); Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Justin Stitt <justinstitt@google.com> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Petr Mladek <pmladek@suse.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Yun Zhou <redacted> Cc: Jacob Keller <jacob.e.keller@intel.com> Cc: Zhen Lei <redacted> Cc: linux-trace-kernel@vger.kernel.org Signed-off-by: Kees Cook <redacted> --- include/linux/seq_buf.h | 19 +++++++++++++++---- kernel/trace/trace.c | 11 +---------- lib/seq_buf.c | 4 +--- 3 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index 8483e4b2d0d2..8896b830eb3d 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h@@ -21,9 +21,16 @@ struct seq_buf { size_t len; }; +#define DECLARE_SEQ_BUF(NAME, SIZE) \ + char __ ## NAME ## _buffer[SIZE] = ""; \ + struct seq_buf NAME = { .buffer = &__ ## NAME ## _buffer, \ + .size = SIZE } + static inline void seq_buf_clear(struct seq_buf *s) { s->len = 0; + if (s->size) + s->buffer[0] = '\0'; } static inline void
@@ -69,8 +76,8 @@ static inline unsigned int seq_buf_used(struct seq_buf *s) } /** - * seq_buf_terminate - Make sure buffer is nul terminated - * @s: the seq_buf descriptor to terminate. + * seq_buf_cstr - get %NUL-terminated C string from seq_buf + * @s: the seq_buf handle * * This makes sure that the buffer in @s is nul terminated and * safe to read as a string.
@@ -81,16 +88,20 @@ static inline unsigned int seq_buf_used(struct seq_buf *s) * * After this function is called, s->buffer is safe to use * in string operations. + * + * Returns @s->buf after making sure it is terminated. */ -static inline void seq_buf_terminate(struct seq_buf *s) +static inline char *seq_buf_cstr(struct seq_buf *s) { if (WARN_ON(s->size == 0)) - return; + return ""; if (seq_buf_buffer_left(s)) s->buffer[s->len] = 0; else s->buffer[s->size - 1] = 0; + + return s->buffer; } /**
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d629065c2383..d83f36dc4bf8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -3828,15 +3828,6 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str, return false; } -static const char *show_buffer(struct trace_seq *s) -{ - struct seq_buf *seq = &s->seq; - - seq_buf_terminate(seq); - - return seq->buffer; -} - static DEFINE_STATIC_KEY_FALSE(trace_no_verify); static int test_can_verify_check(const char *fmt, ...)
@@ -3976,7 +3967,7 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, */ if (WARN_ONCE(!trace_safe_str(iter, str, star, len), "fmt: '%s' current_buffer: '%s'", - fmt, show_buffer(&iter->seq))) { + fmt, seq_buf_cstr(&iter->seq.seq))) { int ret; /* Try to safely read the string */
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index b7477aefff53..165caed5a74e 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c@@ -109,9 +109,7 @@ void seq_buf_do_printk(struct seq_buf *s, const char *lvl) if (s->size == 0 || s->len == 0) return; - seq_buf_terminate(s); - - start = s->buffer; + start = seq_buf_cstr(s); while ((lf = strchr(start, '\n'))) { int len = lf - start + 1;
--
2.34.1