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tracing: Add length protection to histogram string copies

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The string copies to the histogram storage has a max size of 256 bytes
(defined by MAX_FILTER_STR_VAL). Only the string size of the event field
needs to be copied to the event storage, but no more than what is in the
event storage. Although nothing should be bigger than 256 bytes, there's
no protection against overwriting of the storage if one day there is.

Copy no more than the destination size, and enforce it.

Also had to turn MAX_FILTER_STR_VAL into an unsigned int, to keep the
min() comparison of the string sizes of comparable types.

Link: https://lore.kernel.org/all/CAHk-=wjREUihCGrtRBwfX47y_KrLCGjiq3t6QtoNJpmVrAEb1w@mail.gmail.com/
Link: https://lkml.kernel.org/r/20211114132834.183429a4@rorschach.local.home

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 63f84ae6b8 ("tracing/histogram: Do not copy the fixed-size char array field over the field size")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2021-11-14 13:28:34 -05:00
parent 1cab6bce42
commit 938aa33f14
2 changed files with 8 additions and 3 deletions
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2
include/linux/trace_events.h
View File

@ -673,7 +673,7 @@ struct trace_event_file {
#define PERF_MAX_TRACE_SIZE 8192
#define MAX_FILTER_STR_VAL 256 /* Should handle KSYM_SYMBOL_LEN */
#define MAX_FILTER_STR_VAL 256U /* Should handle KSYM_SYMBOL_LEN */
enum event_trigger_type {
ETT_NONE = (0),

9
kernel/trace/trace_events_hist.c
View File

@ -3026,8 +3026,10 @@ static inline void __update_field_vars(struct tracing_map_elt *elt,
if (val->flags & HIST_FIELD_FL_STRING) {
char *str = elt_data->field_var_str[j++];
char *val_str = (char *)(uintptr_t)var_val;
unsigned int size;
strscpy(str, val_str, val->size);
size = min(val->size, STR_VAR_LEN_MAX);
strscpy(str, val_str, size);
var_val = (u64)(uintptr_t)str;
}
tracing_map_set_var(elt, var_idx, var_val);
@ -4914,6 +4916,7 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
if (hist_field->flags & HIST_FIELD_FL_STRING) {
unsigned int str_start, var_str_idx, idx;
char *str, *val_str;
unsigned int size;
str_start = hist_data->n_field_var_str +
hist_data->n_save_var_str;
@ -4922,7 +4925,9 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
str = elt_data->field_var_str[idx];
val_str = (char *)(uintptr_t)hist_val;
strscpy(str, val_str, hist_field->size);
size = min(hist_field->size, STR_VAR_LEN_MAX);
strscpy(str, val_str, size);
hist_val = (u64)(uintptr_t)str;
}