| Message ID | 20240227125706.04279ac2@gandalf.local.home (mailing list archive) |
|---|---|
| State | Rejected |
| Headers | show |
| Series | tracing: Prevent trace_marker being bigger than unsigned short | expand |
On Tue, 27 Feb 2024 12:57:06 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > The trace_marker write goes into the ring buffer. A test was added to > write a string as big as the sub-buffer of the ring buffer to see if it > would work. A sub-buffer is typically PAGE_SIZE in length. > > On PowerPC architecture, the ftrace selftest for trace_marker started to > fail. This was due to PowerPC having a PAGE_SIZE of 65536 and not 4096. It > would try to write a string that was around 63000 bytes in size. This gave > the following warning: > > ------------[ cut here ]------------ > precision 63492 too large > WARNING: CPU: 15 PID: 2538829 at lib/vsprintf.c:2721 set_precision+0x68/0xa4 > Modules linked in: > CPU: 15 PID: 2538829 Comm: awk Tainted: G M O K 6.8.0-rc5-gfca7526b7d89 #1 > Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NH1060_018) hv:phyp pSeries > NIP: c000000000f57c34 LR: c000000000f57c30 CTR: c000000000f5cdf0 > REGS: c000000a58e4f5f0 TRAP: 0700 Tainted: G M O K (6.8.0-rc5-gfca7526b7d89) > MSR: 8000000002029033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 48000824 XER: 00000005 > CFAR: c00000000016154c IRQMASK: 0 > GPR00: c000000000f57c30 c000000a58e4f890 c000000001482800 0000000000000019 > GPR04: 0000000100011559 c000000a58e4f660 c000000a58e4f658 0000000000000027 > GPR08: c000000e84e37c10 0000000000000001 0000000000000027 c000000002a47e50 > GPR12: 0000000000000000 c000000e87bf7300 0000000000000000 0000000000000000 > GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR20: c0000004a43ec590 0000000000400cc0 0000000000000003 c0000000012c3e65 > GPR24: c000000a58e4fa18 0000000000000025 0000000000000020 000000000001ff97 > GPR28: c0000001168a00dd c0000001168c0074 c000000a58e4f920 000000000000f804 > NIP [c000000000f57c34] set_precision+0x68/0xa4 > LR [c000000000f57c30] set_precision+0x64/0xa4 > Call Trace: > [c000000a58e4f890] [c000000000f57c30] set_precision+0x64/0xa4 (unreliable) > [c000000a58e4f900] [c000000000f5ccc4] vsnprintf+0x198/0x4c8 > [c000000a58e4f980] [c000000000f53228] seq_buf_vprintf+0x50/0xa0 > [c000000a58e4f9b0] [c00000000031cec0] trace_seq_printf+0x60/0xe0 > [c000000a58e4f9e0] [c00000000031b5f0] trace_print_print+0x78/0xa4 > [c000000a58e4fa60] [c0000000003133a4] print_trace_line+0x2ac/0x6d8 > [c000000a58e4fb20] [c0000000003145c0] s_show+0x58/0x2c0 > [c000000a58e4fba0] [c0000000005dfb2c] seq_read_iter+0x448/0x618 > [c000000a58e4fc70] [c0000000005dfe08] seq_read+0x10c/0x174 > [c000000a58e4fd10] [c00000000059a7e0] vfs_read+0xe0/0x39c > [c000000a58e4fdc0] [c00000000059b59c] ksys_read+0x7c/0x140 > [c000000a58e4fe10] [c000000000035d74] system_call_exception+0x134/0x330 > [c000000a58e4fe50] [c00000000000d6a0] system_call_common+0x160/0x2e4 > > The problem was that in trace_print_print() that reads the trace_marker > write data had the following code: > > int max = iter->ent_size - offsetof(struct print_entry, buf); > > [..] > trace_seq_printf(s, ": %.*s", max, field->buf); > > Where "max" was the size of the entry. Now that the write to trace_marker > can be as big as what the sub-buffer can hold, and the sub-buffer for > powerpc is 64K in size, the "max" value was: 63492, and that was passed to > trace_seq_printf() which eventually calls vsnprintf() with the same format > and parameters. > > The max "precision" that "%.*s" can be is max signed short (32767) where > 63492 happens to be greater than. > > Prevent the max size written by trace_marker to be greater than what a > signed short can hold. This looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thank you, > > Link: https://lore.kernel.org/all/C7E7AF1A-D30F-4D18-B8E5-AF1EF58004F5@linux.ibm.com/ > > Reported-by: Sachin Sant <sachinp@linux.ibm.com> > Tested-by: Sachin Sant <sachinp@linux.ibm.com> > Fixes: 8ec90be7f15f ("tracing: Allow for max buffer data size trace_marker writes") > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/trace.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 8198bfc54b58..1606fa99367b 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -7310,7 +7310,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > /* Used in tracing_mark_raw_write() as well */ > #define FAULTED_STR "<faulted>" > #define FAULTED_SIZE (sizeof(FAULTED_STR) - 1) /* '\0' is already accounted for */ > - > +#ifndef SHORT_MAX > +#define SHORT_MAX ((1<<15) - 1) > +#endif > if (tracing_disabled) > return -EINVAL; > > @@ -7328,6 +7330,16 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, > if (cnt < FAULTED_SIZE) > size += FAULTED_SIZE - cnt; > > + /* > + * trace_print_print() uses vsprintf() to determine the size via > + * the precision format "%.*s" which can not be greater than > + * a signed short. > + */ > + if (size > SHORT_MAX) { > + cnt -= size - SHORT_MAX; > + goto again; > + } > + > if (size > TRACE_SEQ_BUFFER_SIZE) { > cnt -= size - TRACE_SEQ_BUFFER_SIZE; > goto again; > -- > 2.43.0 >
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8198bfc54b58..1606fa99367b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7310,7 +7310,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, /* Used in tracing_mark_raw_write() as well */ #define FAULTED_STR "<faulted>" #define FAULTED_SIZE (sizeof(FAULTED_STR) - 1) /* '\0' is already accounted for */ - +#ifndef SHORT_MAX +#define SHORT_MAX ((1<<15) - 1) +#endif if (tracing_disabled) return -EINVAL; @@ -7328,6 +7330,16 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (cnt < FAULTED_SIZE) size += FAULTED_SIZE - cnt; + /* + * trace_print_print() uses vsprintf() to determine the size via + * the precision format "%.*s" which can not be greater than + * a signed short. + */ + if (size > SHORT_MAX) { + cnt -= size - SHORT_MAX; + goto again; + } + if (size > TRACE_SEQ_BUFFER_SIZE) { cnt -= size - TRACE_SEQ_BUFFER_SIZE; goto again;