From: Kees Cook <keescook@chromium.org> stable inclusion from stable-v6.6.70 commit 6920e362bc080d045dd1eca431c7819f22014a81 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBJ835 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit dcc4e5728eeaeda84878ca0018758cff1abfca21 ] 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 directly after terminating it in the refactored seq_buf_terminate(), now known as seq_buf_str(): do_something(seq_buf_str(s)); Link: https://lore.kernel.org/linux-trace-kernel/20231027155634.make.260-kees@kern... Link: https://lore.kernel.org/linux-trace-kernel/20231026194033.it.702-kees@kernel... Cc: Yosry Ahmed <yosryahmed@google.com> 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 <yun.zhou@windriver.com> Cc: Jacob Keller <jacob.e.keller@intel.com> Cc: Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Stable-dep-of: afd2627f727b ("tracing: Check "%s" dereference via the field and not the TP_printk format") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Li Huafei <lihuafei1@huawei.com> --- include/linux/seq_buf.h | 21 +++++++++++++++++---- kernel/trace/trace.c | 11 +---------- lib/seq_buf.c | 4 +--- 3 files changed, 19 insertions(+), 17 deletions(-) diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h index a0fb013cebdf..d9db59f420a4 100644 --- a/include/linux/seq_buf.h +++ b/include/linux/seq_buf.h @@ -21,9 +21,18 @@ 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 +78,8 @@ 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_str - 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 +90,20 @@ 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 const char *seq_buf_str(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 d278b1df6286..88027b3b8158 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3810,15 +3810,6 @@ 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, ...) @@ -3958,7 +3949,7 @@ 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_str(&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..23518f77ea9c 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_str(s); while ((lf = strchr(start, '\n'))) { int len = lf - start + 1; -- 2.25.1