+ zram-protect-recomp_algorithm_show-with-init_lock.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: zram: protect recomp_algorithm_show() with ->init_lock
has been added to the -mm mm-new branch.  Its filename is
     zram-protect-recomp_algorithm_show-with-init_lock.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-protect-recomp_algorithm_show-with-init_lock.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: zram: protect recomp_algorithm_show() with ->init_lock
Date: Tue, 5 Aug 2025 19:19:29 +0900

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.

Link: https://lkml.kernel.org/r/20250805101946.1774112-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reported-by: Seyediman Seyedarab <imandevel@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/zram/zram_drv.c |   23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

--- a/drivers/block/zram/zram_drv.c~zram-protect-recomp_algorithm_show-with-init_lock
+++ a/drivers/block/zram/zram_drv.c
@@ -1225,18 +1225,6 @@ static void comp_algorithm_set(struct zr
 	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(struc
 				   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(str
 	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;
 }
 
_

Patches currently in -mm which might be from senozhatsky@chromium.org are

zram-protect-recomp_algorithm_show-with-init_lock.patch