From 7cbce1eaeb783af9e88fc5cebe9b18d46d9030bd Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Tue, 5 Aug 2025 19:19:29 +0900 Subject: [PATCH] zram: protect recomp_algorithm_show() with ->init_lock sysfs handlers should be called under ->init_lock and are not supposed to unlock it until return, otherwise e.g. a concurrent reset() can occur. There is one handler that breaks that rule: recomp_algorithm_show(). Move ->init_lock handling outside of __comp_algorithm_show() (also drop it and call zcomp_available_show() directly) so that the entire recomp_algorithm_show() loop is protected by the lock, as opposed to protecting individual iterations. The patch does not need to go to -stable, as it does not fix any runtime errors (at least I can't think of any). It makes recomp_algorithm_show() "atomic" w.r.t. zram reset() (just like the rest of zram sysfs show() handlers), that's a pretty minor change. Link: https://lkml.kernel.org/r/20250805101946.1774112-1-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Reported-by: Seyediman Seyedarab Suggested-by: Seyediman Seyedarab Cc: Jens Axboe Cc: Minchan Kim Signed-off-by: Andrew Morton --- drivers/block/zram/zram_drv.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 8acad3cc6e6ea..9ac271b82780a 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1225,18 +1225,6 @@ static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg) zram->comp_algs[prio] = alg; } -static ssize_t __comp_algorithm_show(struct zram *zram, u32 prio, - char *buf, ssize_t at) -{ - ssize_t sz; - - down_read(&zram->init_lock); - sz = zcomp_available_show(zram->comp_algs[prio], buf, at); - up_read(&zram->init_lock); - - return sz; -} - static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf) { char *compressor; @@ -1387,8 +1375,12 @@ static ssize_t comp_algorithm_show(struct device *dev, char *buf) { struct zram *zram = dev_to_zram(dev); + ssize_t sz; - return __comp_algorithm_show(zram, ZRAM_PRIMARY_COMP, buf, 0); + down_read(&zram->init_lock); + sz = zcomp_available_show(zram->comp_algs[ZRAM_PRIMARY_COMP], buf, 0); + up_read(&zram->init_lock); + return sz; } static ssize_t comp_algorithm_store(struct device *dev, @@ -1412,14 +1404,15 @@ static ssize_t recomp_algorithm_show(struct device *dev, ssize_t sz = 0; u32 prio; + down_read(&zram->init_lock); for (prio = ZRAM_SECONDARY_COMP; prio < ZRAM_MAX_COMPS; prio++) { if (!zram->comp_algs[prio]) continue; sz += sysfs_emit_at(buf, sz, "#%d: ", prio); - sz += __comp_algorithm_show(zram, prio, buf, sz); + sz += zcomp_available_show(zram->comp_algs[prio], buf, sz); } - + up_read(&zram->init_lock); return sz; } -- 2.47.3