There is a rare NULL pointer bug in mem_used_total_show() in concurrent
situation, like this:
zram is not initialized, process A is a mem_used_total reader which runs
periodicity, while process B try to init zram.
process A process B
access meta, get a NULL value
init zram, done
init_done() is true
access meta->mem_pool, get a NULL pointer BUG
This patch fixes this issue.
Signed-off-by: Weijie Yang <[email protected]>
---
drivers/block/zram/zram_drv.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 64dd79a..2ffd7d8 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -99,11 +99,12 @@ static ssize_t mem_used_total_show(struct device *dev,
{
u64 val = 0;
struct zram *zram = dev_to_zram(dev);
- struct zram_meta *meta = zram->meta;
down_read(&zram->init_lock);
- if (init_done(zram))
+ if (init_done(zram)) {
+ struct zram_meta *meta = zram->meta;
val = zs_get_total_pages(meta->mem_pool);
+ }
up_read(&zram->init_lock);
return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
--
1.7.0.4
--
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