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kcsan: Show location access was reordered to

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Also show the location the access was reordered to. An example report:

| ==================================================================
| BUG: KCSAN: data-race in test_kernel_wrong_memorder / test_kernel_wrong_memorder
|
| read-write to 0xffffffffc01e61a8 of 8 bytes by task 2311 on cpu 5:
|  test_kernel_wrong_memorder+0x57/0x90
|  access_thread+0x99/0xe0
|  kthread+0x2ba/0x2f0
|  ret_from_fork+0x22/0x30
|
| read-write (reordered) to 0xffffffffc01e61a8 of 8 bytes by task 2310 on cpu 7:
|  test_kernel_wrong_memorder+0x57/0x90
|  access_thread+0x99/0xe0
|  kthread+0x2ba/0x2f0
|  ret_from_fork+0x22/0x30
|   |
|   +-> reordered to: test_kernel_wrong_memorder+0x80/0x90
|
| Reported by Kernel Concurrency Sanitizer on:
| CPU: 7 PID: 2310 Comm: access_thread Not tainted 5.14.0-rc1+ #18
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
| ==================================================================

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Marco Elver 2021-11-30 12:44:16 +01:00 committed by Paul E. McKenney
parent 3cc21a5312
commit be3f6967ec
1 changed files with 23 additions and 12 deletions
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35
kernel/kcsan/report.c
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@ -308,10 +308,12 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
/* /*
* Skips to the first entry that matches the function of @ip, and then replaces * Skips to the first entry that matches the function of @ip, and then replaces
* that entry with @ip, returning the entries to skip. * that entry with @ip, returning the entries to skip with @replaced containing
* the replaced entry.
*/ */
static int static int
replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip) replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip,
unsigned long *replaced)
{ {
unsigned long symbolsize, offset; unsigned long symbolsize, offset;
unsigned long target_func; unsigned long target_func;
@ -330,6 +332,7 @@ replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned lon
func -= offset; func -= offset;
if (func == target_func) { if (func == target_func) {
*replaced = stack_entries[skip];
stack_entries[skip] = ip; stack_entries[skip] = ip;
return skip; return skip;
} }
@ -342,9 +345,10 @@ fallback:
} }
static int static int
sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip) sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip,
unsigned long *replaced)
{ {
return ip ? replace_stack_entry(stack_entries, num_entries, ip) : return ip ? replace_stack_entry(stack_entries, num_entries, ip, replaced) :
get_stack_skipnr(stack_entries, num_entries); get_stack_skipnr(stack_entries, num_entries);
} }
@ -360,6 +364,14 @@ static int sym_strcmp(void *addr1, void *addr2)
return strncmp(buf1, buf2, sizeof(buf1)); return strncmp(buf1, buf2, sizeof(buf1));
} }
static void
print_stack_trace(unsigned long stack_entries[], int num_entries, unsigned long reordered_to)
{
stack_trace_print(stack_entries, num_entries, 0);
if (reordered_to)
pr_err(" |\n +-> reordered to: %pS\n", (void *)reordered_to);
}
static void print_verbose_info(struct task_struct *task) static void print_verbose_info(struct task_struct *task)
{ {
if (!task) if (!task)
@ -378,10 +390,12 @@ static void print_report(enum kcsan_value_change value_change,
struct other_info *other_info, struct other_info *other_info,
u64 old, u64 new, u64 mask) u64 old, u64 new, u64 mask)
{ {
unsigned long reordered_to = 0;
unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 }; unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 };
int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1); int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1);
int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip); int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip, &reordered_to);
unsigned long this_frame = stack_entries[skipnr]; unsigned long this_frame = stack_entries[skipnr];
unsigned long other_reordered_to = 0;
unsigned long other_frame = 0; unsigned long other_frame = 0;
int other_skipnr = 0; /* silence uninit warnings */ int other_skipnr = 0; /* silence uninit warnings */
@ -394,7 +408,7 @@ static void print_report(enum kcsan_value_change value_change,
if (other_info) { if (other_info) {
other_skipnr = sanitize_stack_entries(other_info->stack_entries, other_skipnr = sanitize_stack_entries(other_info->stack_entries,
other_info->num_stack_entries, other_info->num_stack_entries,
other_info->ai.ip); other_info->ai.ip, &other_reordered_to);
other_frame = other_info->stack_entries[other_skipnr]; other_frame = other_info->stack_entries[other_skipnr];
/* @value_change is only known for the other thread */ /* @value_change is only known for the other thread */
@ -434,10 +448,9 @@ static void print_report(enum kcsan_value_change value_change,
other_info->ai.cpu_id); other_info->ai.cpu_id);
/* Print the other thread's stack trace. */ /* Print the other thread's stack trace. */
stack_trace_print(other_info->stack_entries + other_skipnr, print_stack_trace(other_info->stack_entries + other_skipnr,
other_info->num_stack_entries - other_skipnr, other_info->num_stack_entries - other_skipnr,
0); other_reordered_to);
if (IS_ENABLED(CONFIG_KCSAN_VERBOSE)) if (IS_ENABLED(CONFIG_KCSAN_VERBOSE))
print_verbose_info(other_info->task); print_verbose_info(other_info->task);
@ -451,9 +464,7 @@ static void print_report(enum kcsan_value_change value_change,
get_thread_desc(ai->task_pid), ai->cpu_id); get_thread_desc(ai->task_pid), ai->cpu_id);
} }
/* Print stack trace of this thread. */ /* Print stack trace of this thread. */
stack_trace_print(stack_entries + skipnr, num_stack_entries - skipnr, print_stack_trace(stack_entries + skipnr, num_stack_entries - skipnr, reordered_to);
0);
if (IS_ENABLED(CONFIG_KCSAN_VERBOSE)) if (IS_ENABLED(CONFIG_KCSAN_VERBOSE))
print_verbose_info(current); print_verbose_info(current);