Commit a8772fad authored by Tetsuo Handa's avatar Tetsuo Handa
Browse files

tomoyo: Use atomic_t for statistics counter 

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: default avatarsyzbot <syzbot+efea72d4a0a1d03596cd@syzkaller.appspotmail.com>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
parent 738d2902

security/tomoyo/common.c

+4 −7
Original line number Diff line number Diff line
@@ -2322,9 +2322,9 @@ static const char * const tomoyo_memory_headers[TOMOYO_MAX_MEMORY_STAT] = { 
	[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];



/**
@@ -2336,10 +2336,7 @@ static time64_t tomoyo_stat_modified[TOMOYO_MAX_POLICY_STAT]; 
 */

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();

}
@@ -2360,7 +2357,7 @@ static void tomoyo_read_stat(struct tomoyo_io_buffer *head) 
	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;

CRA Git | Maintained and supported by SUSTech CRA and CCSE