[ltt-dev] [PATCH UST] serialize string input robustness
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Sun Aug 15 19:11:37 EDT 2010
Make sure we handle concurrently modified input strings gracefully.
Adds ust_buffers_strncpy interface. It fixes up the string if it does not fills
exactly the space allocated. Ensures the string ends with \0.
Removes unused "_ust_buffers_write" at the same time.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
---
include/ust/probe.h | 4 +-
libust/buffers.c | 78 +++++++++++++++++++++++++++++++++++++------------
libust/buffers.h | 82 +++++++++++++++++++++++++++++++++++++++++++++++-----
libust/serialize.c | 67 ++++++++++++++++++++++++++++++++++--------
libust/tracer.h | 3 +
5 files changed, 193 insertions(+), 41 deletions(-)
Index: ust/libust/buffers.h
===================================================================
--- ust.orig/libust/buffers.h 2010-08-15 18:38:35.000000000 -0400
+++ ust/libust/buffers.h 2010-08-15 18:38:43.000000000 -0400
@@ -513,22 +513,90 @@ static __inline__ void ltt_commit_slot(
ltt_write_commit_counter(chan, buf, endidx, buf_offset, commit_count, data_size);
}
-void _ust_buffers_write(struct ust_buffer *buf, size_t offset,
- const void *src, size_t len, ssize_t cpy);
+void _ust_buffers_strncpy_fixup(struct ust_buffer *buf, size_t offset,
+ size_t len, size_t copied, int terminated);
static __inline__ int ust_buffers_write(struct ust_buffer *buf, size_t offset,
const void *src, size_t len)
{
- size_t cpy;
size_t buf_offset = BUFFER_OFFSET(offset, buf->chan);
assert(buf_offset < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
+ assert(buf_offset + len < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
- cpy = min_t(size_t, len, buf->buf_size - buf_offset);
- ust_buffers_do_copy(buf->buf_data + buf_offset, src, cpy);
+ ust_buffers_do_copy(buf->buf_data + buf_offset, src, len);
- if (unlikely(len != cpy))
- _ust_buffers_write(buf, buf_offset, src, len, cpy);
+ return len;
+}
+
+/*
+ * ust_buffers_do_memset - write character into dest.
+ * @dest: destination
+ * @src: source character
+ * @len: length to write
+ */
+static __inline__
+void ust_buffers_do_memset(void *dest, char src, size_t len)
+{
+ /*
+ * What we really want here is an __inline__ memset, but we
+ * don't have constants, so gcc generally uses a function call.
+ */
+ for (; len > 0; len--)
+ *(u8 *)dest++ = src;
+}
+
+/*
+ * ust_buffers_do_strncpy - copy a string up to a certain number of bytes
+ * @dest: destination
+ * @src: source
+ * @len: max. length to copy
+ * @terminated: output string ends with \0 (output)
+ *
+ * returns the number of bytes copied. Does not finalize with \0 if len is
+ * reached.
+ */
+static __inline__
+size_t ust_buffers_do_strncpy(void *dest, const void *src, size_t len,
+ int *terminated)
+{
+ size_t orig_len = len;
+
+ *terminated = 0;
+ /*
+ * What we really want here is an __inline__ strncpy, but we
+ * don't have constants, so gcc generally uses a function call.
+ */
+ for (; len > 0; len--) {
+ *(u8 *)dest = LOAD_SHARED(*(const u8 *)src);
+ /* Check with dest, because src may be modified concurrently */
+ if (*(const u8 *)dest == '\0') {
+ len--;
+ *terminated = 1;
+ break;
+ }
+ dest++;
+ src++;
+ }
+ return orig_len - len;
+}
+
+static __inline__
+int ust_buffers_strncpy(struct ust_buffer *buf, size_t offset, const void *src,
+ size_t len)
+{
+ size_t buf_offset = BUFFER_OFFSET(offset, buf->chan);
+ ssize_t copied;
+ int terminated;
+
+ assert(buf_offset < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
+ assert(buf_offset + len < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
+
+ copied = ust_buffers_do_strncpy(buf->buf_data + buf_offset,
+ src, len, &terminated);
+ if (unlikely(copied < len || !terminated))
+ _ust_buffers_strncpy_fixup(buf, offset, len, copied,
+ terminated);
return len;
}
Index: ust/libust/serialize.c
===================================================================
--- ust.orig/libust/serialize.c 2010-08-15 18:38:35.000000000 -0400
+++ ust/libust/serialize.c 2010-08-15 18:38:43.000000000 -0400
@@ -43,6 +43,12 @@
#include "usterr.h"
#include "ust_snprintf.h"
+/*
+ * Because UST core defines a non-const PAGE_SIZE, define PAGE_SIZE_STATIC here.
+ * It is just an approximation for the tracer stack.
+ */
+#define PAGE_SIZE_STATIC 4096
+
enum ltt_type {
LTT_TYPE_SIGNED_INT,
LTT_TYPE_UNSIGNED_INT,
@@ -50,6 +56,16 @@ enum ltt_type {
LTT_TYPE_NONE,
};
+/*
+ * Special stack for the tracer. Keeps serialization offsets for each field.
+ * Per-thread. Deals with reentrancy from signals by simply ensuring that
+ * interrupting signals put the stack back to its original position.
+ */
+#define TRACER_STACK_LEN (PAGE_SIZE_STATIC / sizeof(unsigned long))
+static unsigned long __thread tracer_stack[TRACER_STACK_LEN];
+
+static unsigned int __thread tracer_stack_pos;
+
#define LTT_ATTRIBUTE_NETWORK_BYTE_ORDER (1<<1)
/*
@@ -349,7 +365,9 @@ static inline size_t serialize_trace_dat
size_t buf_offset,
char trace_size, enum ltt_type trace_type,
char c_size, enum ltt_type c_type,
- int *largest_align, va_list *args)
+ unsigned int *stack_pos_ctx,
+ int *largest_align,
+ va_list *args)
{
union {
unsigned long v_ulong;
@@ -405,10 +423,20 @@ static inline size_t serialize_trace_dat
tmp.v_string.s = va_arg(*args, const char *);
if ((unsigned long)tmp.v_string.s < PAGE_SIZE)
tmp.v_string.s = "<NULL>";
- tmp.v_string.len = strlen(tmp.v_string.s)+1;
+ if (!buf) {
+ /*
+ * Reserve tracer stack entry.
+ */
+ tracer_stack_pos++;
+ assert(tracer_stack_pos <= TRACER_STACK_LEN);
+ barrier();
+ tracer_stack[*stack_pos_ctx] =
+ strlen(tmp.v_string.s) + 1;
+ }
+ tmp.v_string.len = tracer_stack[(*stack_pos_ctx)++];
if (buf)
- ust_buffers_write(buf, buf_offset, tmp.v_string.s,
- tmp.v_string.len);
+ ust_buffers_strncpy(buf, buf_offset, tmp.v_string.s,
+ tmp.v_string.len);
buf_offset += tmp.v_string.len;
goto copydone;
default:
@@ -508,7 +536,9 @@ copydone:
notrace size_t ltt_serialize_data(struct ust_buffer *buf, size_t buf_offset,
struct ltt_serialize_closure *closure,
- void *serialize_private, int *largest_align,
+ void *serialize_private,
+ unsigned int stack_pos_ctx,
+ int *largest_align,
const char *fmt, va_list *args)
{
char trace_size = 0, c_size = 0; /*
@@ -548,7 +578,9 @@ notrace size_t ltt_serialize_data(struct
buf_offset = serialize_trace_data(buf,
buf_offset, trace_size,
trace_type, c_size, c_type,
- largest_align, args);
+ &stack_pos_ctx,
+ largest_align,
+ args);
trace_size = 0;
c_size = 0;
trace_type = LTT_TYPE_NONE;
@@ -566,25 +598,29 @@ notrace size_t ltt_serialize_data(struct
* Assume that the padding for alignment starts at a sizeof(void *) address.
*/
static notrace size_t ltt_get_data_size(struct ltt_serialize_closure *closure,
- void *serialize_private, int *largest_align,
+ void *serialize_private,
+ unsigned int stack_pos_ctx, int *largest_align,
const char *fmt, va_list *args)
{
ltt_serialize_cb cb = closure->callbacks[0];
closure->cb_idx = 0;
return (size_t)cb(NULL, 0, closure, serialize_private,
- largest_align, fmt, args);
+ stack_pos_ctx, largest_align, fmt, args);
}
static notrace
void ltt_write_event_data(struct ust_buffer *buf, size_t buf_offset,
struct ltt_serialize_closure *closure,
- void *serialize_private, int largest_align,
+ void *serialize_private,
+ unsigned int stack_pos_ctx,
+ int largest_align,
const char *fmt, va_list *args)
{
ltt_serialize_cb cb = closure->callbacks[0];
closure->cb_idx = 0;
buf_offset += ltt_align(buf_offset, largest_align);
- cb(buf, buf_offset, closure, serialize_private, NULL, fmt, args);
+ cb(buf, buf_offset, closure, serialize_private, stack_pos_ctx, NULL,
+ fmt, args);
}
@@ -609,6 +645,7 @@ notrace void ltt_vtrace(const struct mar
void *serialize_private = NULL;
int cpu;
unsigned int rflags;
+ unsigned int stack_pos_ctx;
/*
* This test is useful for quickly exiting static tracing when no trace
@@ -622,6 +659,7 @@ notrace void ltt_vtrace(const struct mar
/* Force volatile access. */
STORE_SHARED(ltt_nesting, LOAD_SHARED(ltt_nesting) + 1);
+ stack_pos_ctx = tracer_stack_pos;
barrier();
pdata = (struct ltt_active_marker *)probe_data;
@@ -642,7 +680,8 @@ notrace void ltt_vtrace(const struct mar
*/
largest_align = 1; /* must be non-zero for ltt_align */
data_size = ltt_get_data_size(&closure, serialize_private,
- &largest_align, fmt, &args_copy);
+ stack_pos_ctx, &largest_align,
+ fmt, &args_copy);
largest_align = min_t(int, largest_align, sizeof(void *));
va_end(args_copy);
@@ -698,8 +737,9 @@ notrace void ltt_vtrace(const struct mar
buf_offset = ltt_write_event_header(channel, buf, buf_offset,
eID, data_size, tsc, rflags);
ltt_write_event_data(buf, buf_offset, &closure,
- serialize_private,
- largest_align, fmt, &args_copy);
+ serialize_private,
+ stack_pos_ctx, largest_align,
+ fmt, &args_copy);
va_end(args_copy);
/* Out-of-order commit */
ltt_commit_slot(channel, buf, buf_offset, data_size, slot_size);
@@ -707,6 +747,7 @@ notrace void ltt_vtrace(const struct mar
}
barrier();
+ tracer_stack_pos = stack_pos_ctx;
STORE_SHARED(ltt_nesting, LOAD_SHARED(ltt_nesting) - 1);
rcu_read_unlock(); //ust// rcu_read_unlock_sched_notrace();
Index: ust/libust/buffers.c
===================================================================
--- ust.orig/libust/buffers.c 2010-08-15 18:38:43.000000000 -0400
+++ ust/libust/buffers.c 2010-08-15 18:38:43.000000000 -0400
@@ -70,28 +70,68 @@ static int get_n_cpus(void)
return n_cpus;
}
-/* _ust_buffers_write()
+/**
+ * _ust_buffers_strncpy_fixup - Fix an incomplete string in a ltt_relay buffer.
+ * @buf : buffer
+ * @offset : offset within the buffer
+ * @len : length to write
+ * @copied: string actually copied
+ * @terminated: does string end with \0
*
- * @buf: destination buffer
- * @offset: offset in destination
- * @src: source buffer
- * @len: length of source
- * @cpy: already copied
+ * Fills string with "X" if incomplete.
*/
-
-void _ust_buffers_write(struct ust_buffer *buf, size_t offset,
- const void *src, size_t len, ssize_t cpy)
+void _ust_buffers_strncpy_fixup(struct ust_buffer *buf, size_t offset,
+ size_t len, size_t copied, int terminated)
{
- do {
- len -= cpy;
- src += cpy;
- offset += cpy;
-
- WARN_ON(offset >= buf->buf_size);
-
- cpy = min_t(size_t, len, buf->buf_size - offset);
- ust_buffers_do_copy(buf->buf_data + offset, src, cpy);
- } while (unlikely(len != cpy));
+ size_t buf_offset, cpy;
+
+ if (copied == len) {
+ /*
+ * Deal with non-terminated string.
+ */
+ assert(!terminated);
+ offset += copied - 1;
+ buf_offset = BUFFER_OFFSET(offset, buf->chan);
+ /*
+ * Underlying layer should never ask for writes across
+ * subbuffers.
+ */
+ assert(buf_offset
+ < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
+ ust_buffers_do_memset(buf->buf_data + buf_offset, '\0', 1);
+ return;
+ }
+
+ /*
+ * Deal with incomplete string.
+ * Overwrite string's \0 with X too.
+ */
+ cpy = copied - 1;
+ assert(terminated);
+ len -= cpy;
+ offset += cpy;
+ buf_offset = BUFFER_OFFSET(offset, buf->chan);
+
+ /*
+ * Underlying layer should never ask for writes across subbuffers.
+ */
+ assert(buf_offset
+ < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
+
+ ust_buffers_do_memset(buf->buf_data + buf_offset,
+ 'X', len);
+
+ /*
+ * Overwrite last 'X' with '\0'.
+ */
+ offset += len - 1;
+ buf_offset = BUFFER_OFFSET(offset, buf->chan);
+ /*
+ * Underlying layer should never ask for writes across subbuffers.
+ */
+ assert(buf_offset
+ < buf->chan->subbuf_size*buf->chan->subbuf_cnt);
+ ust_buffers_do_memset(buf->buf_data + buf_offset, '\0', 1);
}
static int ust_buffers_init_buffer(struct ust_trace *trace,
Index: ust/include/ust/probe.h
===================================================================
--- ust.orig/include/ust/probe.h 2010-08-15 18:38:35.000000000 -0400
+++ ust/include/ust/probe.h 2010-08-15 18:38:43.000000000 -0400
@@ -28,7 +28,9 @@ struct ust_buffer;
typedef size_t (*ltt_serialize_cb)(struct ust_buffer *buf, size_t buf_offset,
struct ltt_serialize_closure *closure,
- void *serialize_private, int *largest_align,
+ void *serialize_private,
+ unsigned int stack_pos_ctx,
+ int *largest_align,
const char *fmt, va_list *args);
struct ltt_available_probe {
Index: ust/libust/tracer.h
===================================================================
--- ust.orig/libust/tracer.h 2010-08-15 18:38:35.000000000 -0400
+++ ust/libust/tracer.h 2010-08-15 18:38:43.000000000 -0400
@@ -65,7 +65,8 @@ struct ltt_serialize_closure {
extern size_t ltt_serialize_data(struct ust_buffer *buf, size_t buf_offset,
struct ltt_serialize_closure *closure,
void *serialize_private,
- int *largest_align, const char *fmt, va_list *args);
+ unsigned int stack_pos_ctx, int *largest_align,
+ const char *fmt, va_list *args);
struct ltt_probe_private_data {
struct ust_trace *trace; /*
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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