[BUGFIX PATCH v2.1] tracing: probeevent: Fix to support minus offset from symbol

From: Masami Hiramatsu
Date: Thu Feb 22 2018 - 02:45:31 EST


In Documentation/trace/kprobetrace.txt, it says

@SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)

However, the parser doesn't parse minus offset correctly, since
commit 2fba0c8867af ("tracing/kprobes: Fix probe offset to be
unsigned") drops minus ("-") offset support for kprobe probe
address usage.

This fixes the traceprobe_split_symbol_offset() to parse minus
offset again with checking the offset range, and add a minus
offset check in kprobe probe address usage.

Fixes: 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned")
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
Changes in v2.1:
- Fix to ensure the offset value is less than LONG_MAX.
- Fail if the offset is minus when traceprobe_split_symbol_offset()
is used for the probe address.
- Add Fixes tag.
---
kernel/trace/trace_kprobe.c | 4 ++--
kernel/trace/trace_probe.c | 15 ++++++++++-----
kernel/trace/trace_probe.h | 2 +-
3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5ce9b8cf7be3..b5b1d8aa47d6 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -667,7 +667,7 @@ static int create_trace_kprobe(int argc, char **argv)
char *symbol = NULL, *event = NULL, *group = NULL;
int maxactive = 0;
char *arg;
- unsigned long offset = 0;
+ long offset = 0;
void *addr = NULL;
char buf[MAX_EVENT_NAME_LEN];

@@ -755,7 +755,7 @@ static int create_trace_kprobe(int argc, char **argv)
symbol = argv[1];
/* TODO: support .init module functions */
ret = traceprobe_split_symbol_offset(symbol, &offset);
- if (ret) {
+ if (ret || offset < 0) {
pr_info("Failed to parse either an address or a symbol.\n");
return ret;
}
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index d59357308677..ec3856147fdd 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -320,21 +320,26 @@ static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
}

/* Split symbol and offset. */
-int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
+int traceprobe_split_symbol_offset(char *symbol, long *offset)
{
+ unsigned long ul;
char *tmp;
int ret;

if (!offset)
return -EINVAL;

- tmp = strchr(symbol, '+');
+ tmp = strpbrk(symbol, "+-");
if (tmp) {
- /* skip sign because kstrtoul doesn't accept '+' */
- ret = kstrtoul(tmp + 1, 0, offset);
+ ret = kstrtoul(tmp + 1, 0, &ul);
if (ret)
return ret;
-
+ if (ul > LONG_MAX)
+ return -E2BIG;
+ if (*tmp == '-')
+ *offset = -ul;
+ else
+ *offset = ul;
*tmp = '\0';
} else
*offset = 0;
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 0745f895f780..75daff22ccea 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -365,7 +365,7 @@ extern int traceprobe_conflict_field_name(const char *name,
extern void traceprobe_update_arg(struct probe_arg *arg);
extern void traceprobe_free_probe_arg(struct probe_arg *arg);

-extern int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset);
+extern int traceprobe_split_symbol_offset(char *symbol, long *offset);

/* Sum up total data length for dynamic arraies (strings) */
static nokprobe_inline int