[PATCH] PPC64 rtasd: window when error_log_cnt could get zeroed

From: Paul Mackerras
Date: Mon Nov 15 2004 - 00:04:20 EST


This patch is from Jake Moilanen <moilanen@xxxxxxxxxxxxxx>.

There appears to be a hole that if we get an log_error() call, that we
could zero out our error log count in nvram.

When rtasd() starts up, it turns on the logging via 'no_more_logging =
0'. If we get a log_error() call after that is set but before
nvram_read_error_log has actually read nvram to set error_log_cnt, the
log_error() call will write back to nvram a uninitialized error_log_cnt
value, and wipe out our sequence number.

To close the hole, simply move the 'no_more_logging = 0' till after
nvram sets error_log_cnt but before pSeries_log_error is called.

I also changed the 'no_more_logging' variable to be 'no_logging' since
it's not only used when we stop logging now. I also removed the
"volatile" part of no_more_logging, since it's unneeded.

Signed-off-by: Jake Moilanen <moilanen@xxxxxxxxxxxxxx>
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>

diff -puN arch/ppc64/kernel/rtasd.c~rtasd-no_more_logging-race arch/ppc64/kernel/rtasd.c
--- linux-2.6-bk/arch/ppc64/kernel/rtasd.c~rtasd-no_more_logging-race Mon Nov 8 11:51:11 2004
+++ linux-2.6-bk-moilanen/arch/ppc64/kernel/rtasd.c Mon Nov 8 12:19:47 2004
@@ -48,7 +48,7 @@ static unsigned int rtas_error_log_buffe

static int full_rtas_msgs = 0;

-extern volatile int no_more_logging;
+extern int no_logging;

volatile int error_log_cnt = 0;

@@ -213,7 +213,7 @@ void pSeries_log_error(char *buf, unsign
}

/* Write error to NVRAM */
- if (!no_more_logging && !(err_type & ERR_FLAG_BOOT))
+ if (!no_logging && !(err_type & ERR_FLAG_BOOT))
nvram_write_error_log(buf, len, err_type);

/*
@@ -225,8 +225,8 @@ void pSeries_log_error(char *buf, unsign
printk_log_rtas(buf, len);

/* Check to see if we need to or have stopped logging */
- if (fatal || no_more_logging) {
- no_more_logging = 1;
+ if (fatal || no_logging) {
+ no_logging = 1;
spin_unlock_irqrestore(&rtasd_log_lock, s);
return;
}
@@ -299,7 +299,7 @@ static ssize_t rtas_log_read(struct file

spin_lock_irqsave(&rtasd_log_lock, s);
/* if it's 0, then we know we got the last one (the one in NVRAM) */
- if (rtas_log_size == 0 && !no_more_logging)
+ if (rtas_log_size == 0 && !no_logging)
nvram_clear_error_log();
spin_unlock_irqrestore(&rtasd_log_lock, s);

@@ -417,9 +417,6 @@ static int rtasd(void *unused)
goto error;
}

- /* We can use rtas_log_buf now */
- no_more_logging = 0;
-
printk(KERN_ERR "RTAS daemon started\n");

DEBUG("will sleep for %d jiffies\n", (HZ*60/rtas_event_scan_rate) / 2);
@@ -428,6 +425,10 @@ static int rtasd(void *unused)
memset(logdata, 0, rtas_error_log_max);

rc = nvram_read_error_log(logdata, rtas_error_log_max, &err_type);
+
+ /* We can use rtas_log_buf now */
+ no_logging = 0;
+
if (!rc) {
if (err_type != ERR_FLAG_ALREADY_LOGGED) {
pSeries_log_error(logdata, err_type | ERR_FLAG_BOOT, 0);
diff -puN arch/ppc64/kernel/nvram.c~rtasd-no_more_logging-race arch/ppc64/kernel/nvram.c
--- linux-2.6-bk/arch/ppc64/kernel/nvram.c~rtasd-no_more_logging-race Mon Nov 8 11:52:39 2004
+++ linux-2.6-bk-moilanen/arch/ppc64/kernel/nvram.c Mon Nov 8 12:20:13 2004
@@ -43,9 +43,9 @@ static struct nvram_partition * nvram_pa
static long nvram_error_log_index = -1;
static long nvram_error_log_size = 0;

-volatile int no_more_logging = 1; /* Until we initialize everything,
- * make sure we don't try logging
- * anything */
+int no_logging = 1; /* Until we initialize everything,
+ * make sure we don't try logging
+ * anything */

extern volatile int error_log_cnt;

@@ -640,7 +640,7 @@ int nvram_write_error_log(char * buff, i
loff_t tmp_index;
struct err_log_info info;

- if (no_more_logging) {
+ if (no_logging) {
return -EPERM;
}

-
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