From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> commit a8772fad0172aeae339144598b809fd8d4823331 upstream. syzbot is reporting that there is a race at tomoyo_stat_update() [1]. Although it is acceptable to fail to track exact number of times policy was updated, convert to atomic_t because this is not a hot path. [1] https://syzkaller.appspot.com/bug?id=a4d7b973972eeed410596e6604580e0133b0fc04 Reported-by: syzbot <syzbot+efea72d4a0a1d03596cd@xxxxxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- security/tomoyo/common.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) --- a/security/tomoyo/common.c +++ b/security/tomoyo/common.c @@ -2254,9 +2254,9 @@ static const char * const tomoyo_memory_ [TOMOYO_MEMORY_QUERY] = "query message:", }; -/* Timestamp counter for last updated. */ -static unsigned int tomoyo_stat_updated[TOMOYO_MAX_POLICY_STAT]; /* Counter for number of updates. */ +static atomic_t tomoyo_stat_updated[TOMOYO_MAX_POLICY_STAT]; +/* Timestamp counter for last updated. */ static time64_t tomoyo_stat_modified[TOMOYO_MAX_POLICY_STAT]; /** @@ -2268,10 +2268,7 @@ static time64_t tomoyo_stat_modified[TOM */ void tomoyo_update_stat(const u8 index) { - /* - * I don't use atomic operations because race condition is not fatal. - */ - tomoyo_stat_updated[index]++; + atomic_inc(&tomoyo_stat_updated[index]); tomoyo_stat_modified[index] = ktime_get_real_seconds(); } @@ -2291,7 +2288,7 @@ static void tomoyo_read_stat(struct tomo for (i = 0; i < TOMOYO_MAX_POLICY_STAT; i++) { tomoyo_io_printf(head, "Policy %-30s %10u", tomoyo_policy_headers[i], - tomoyo_stat_updated[i]); + atomic_read(&tomoyo_stat_updated[i])); if (tomoyo_stat_modified[i]) { struct tomoyo_time stamp; tomoyo_convert_time(tomoyo_stat_modified[i], &stamp);
