tracing: Fix synthetic event bug

index c08bde9871ec..5dd0617e5df6 100644
@@ -16,6 +16,7 @@
 #include "trace_dynevent.h"
 #include "trace_probe.h"
 #include "trace_probe_tmpl.h"
+#include "trace_probe_kernel.h"
 
 #define EPROBE_EVENT_SYSTEM "eprobes"
 

@@ -456,29 +457,14 @@ NOKPROBE_SYMBOL(process_fetch_insn)
 static nokprobe_inline int
 fetch_store_strlen_user(unsigned long addr)
 {
-	const void __user *uaddr =  (__force const void __user *)addr;
-
-	return strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
+	return kern_fetch_store_strlen_user(addr);
 }
 
 /* Return the length of string -- including null terminal byte */
 static nokprobe_inline int
 fetch_store_strlen(unsigned long addr)
 {
-	int ret, len = 0;
-	u8 c;
-
-#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
-	if (addr < TASK_SIZE)
-		return fetch_store_strlen_user(addr);
-#endif
-
-	do {
-		ret = copy_from_kernel_nofault(&c, (u8 *)addr + len, 1);
-		len++;
-	} while (c && ret == 0 && len < MAX_STRING_SIZE);
-
-	return (ret < 0) ? ret : len;
+	return kern_fetch_store_strlen(addr);
 }
 
 /*

@@ -488,21 +474,7 @@ fetch_store_strlen(unsigned long addr)
 static nokprobe_inline int
 fetch_store_string_user(unsigned long addr, void *dest, void *base)
 {
-	const void __user *uaddr =  (__force const void __user *)addr;
-	int maxlen = get_loc_len(*(u32 *)dest);
-	void *__dest;
-	long ret;
-
-	if (unlikely(!maxlen))
-		return -ENOMEM;
-
-	__dest = get_loc_data(dest, base);
-
-	ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
-	if (ret >= 0)
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
-
-	return ret;
+	return kern_fetch_store_string_user(addr, dest, base);
 }
 
 /*

@@ -512,29 +484,7 @@ fetch_store_string_user(unsigned long addr, void *dest, void *base)
 static nokprobe_inline int
 fetch_store_string(unsigned long addr, void *dest, void *base)
 {
-	int maxlen = get_loc_len(*(u32 *)dest);
-	void *__dest;
-	long ret;
-
-#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
-	if ((unsigned long)addr < TASK_SIZE)
-		return fetch_store_string_user(addr, dest, base);
-#endif
-
-	if (unlikely(!maxlen))
-		return -ENOMEM;
-
-	__dest = get_loc_data(dest, base);
-
-	/*
-	 * Try to get string again, since the string can be changed while
-	 * probing.
-	 */
-	ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen);
-	if (ret >= 0)
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
-
-	return ret;
+	return kern_fetch_store_string(addr, dest, base);
 }
 
 static nokprobe_inline int

90 lines not on this page · raw message

96 lines not on this page · raw message

index 1d43df29a1f8..77dbd9ff9782 100644
@@ -2,6 +2,8 @@
 #ifndef __TRACE_PROBE_KERNEL_H_
 #define __TRACE_PROBE_KERNEL_H_
 
+#define FAULT_STRING "(fault)"
+
 /*
  * This depends on trace_probe.h, but can not include it due to
  * the way trace_probe_tmpl.h is used by trace_kprobe.c and trace_eprobe.c.

@@ -13,8 +15,16 @@ static nokprobe_inline int
 kern_fetch_store_strlen_user(unsigned long addr)
 {
 	const void __user *uaddr =  (__force const void __user *)addr;
+	int ret;
 
-	return strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
+	ret = strnlen_user_nofault(uaddr, MAX_STRING_SIZE);
+	/*
+	 * strnlen_user_nofault returns zero on fault, insert the
+	 * FAULT_STRING when that occurs.
+	 */
+	if (ret <= 0)
+		return strlen(FAULT_STRING) + 1;
+	return ret;
 }
 
 /* Return the length of string -- including null terminal byte */

@@ -34,7 +44,18 @@ kern_fetch_store_strlen(unsigned long addr)
 		len++;
 	} while (c && ret == 0 && len < MAX_STRING_SIZE);
 
-	return (ret < 0) ? ret : len;
+	/* For faults, return enough to hold the FAULT_STRING */
+	return (ret < 0) ? strlen(FAULT_STRING) + 1 : len;
+}
+
+static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base, int len)
+{
+	if (ret >= 0) {
+		*(u32 *)dest = make_data_loc(ret, __dest - base);
+	} else {
+		strscpy(__dest, FAULT_STRING, len);
+		ret = strlen(__dest) + 1;
+	}
 }
 
 /*

@@ -55,8 +76,7 @@ kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
 	__dest = get_loc_data(dest, base);
 
 	ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
-	if (ret >= 0)
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
+	set_data_loc(ret, dest, __dest, base, maxlen);
 
 	return ret;
 }

@@ -87,8 +107,7 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
 	 * probing.
 	 */
 	ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen);
-	if (ret >= 0)
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
+	set_data_loc(ret, dest, __dest, base, maxlen);
 
 	return ret;
 }

index 5e8c07aef071..e310052dc83c 100644
@@ -17,6 +17,8 @@
 /* for gfp flag names */
 #include <linux/trace_events.h>
 #include <trace/events/mmflags.h>
+#include "trace_probe.h"
+#include "trace_probe_kernel.h"
 
 #include "trace_synth.h"
 

@@ -409,6 +411,7 @@ static unsigned int trace_string(struct synth_trace_event *entry,
 {
 	unsigned int len = 0;
 	char *str_field;
+	int ret;
 
 	if (is_dynamic) {
 		u32 data_offset;

@@ -417,19 +420,27 @@ static unsigned int trace_string(struct synth_trace_event *entry,
 		data_offset += event->n_u64 * sizeof(u64);
 		data_offset += data_size;
 
-		str_field = (char *)entry + data_offset;
-
-		len = strlen(str_val) + 1;
-		strscpy(str_field, str_val, len);
+		len = kern_fetch_store_strlen((unsigned long)str_val);
 
 		data_offset |= len << 16;
 		*(u32 *)&entry->fields[*n_u64] = data_offset;
 
+		ret = kern_fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
+
 		(*n_u64)++;
 	} else {
 		str_field = (char *)&entry->fields[*n_u64];
 
-		strscpy(str_field, str_val, STR_VAR_LEN_MAX);
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+		if ((unsigned long)str_val < TASK_SIZE)
+			ret = strncpy_from_user_nofault(str_field, str_val, STR_VAR_LEN_MAX);
+		else
+#endif
+			ret = strncpy_from_kernel_nofault(str_field, str_val, STR_VAR_LEN_MAX);
+
+		if (ret < 0)
+			strcpy(str_field, FAULT_STRING);
+
 		(*n_u64) += STR_VAR_LEN_MAX / sizeof(u64);
 	}
 

@@ -462,7 +473,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
 		val_idx = var_ref_idx[field_pos];
 		str_val = (char *)(long)var_ref_vals[val_idx];
 
-		len = strlen(str_val) + 1;
+		len = kern_fetch_store_strlen((unsigned long)str_val);
 
 		fields_size += len;
 	}