+ zram-fix-out-of-bounds-access-in-read_block_state.patch added to mm-new branch

The patch titled
     Subject: zram: fix out-of-bounds access in read_block_state()
has been added to the -mm mm-new branch.  Its filename is
     zram-fix-out-of-bounds-access-in-read_block_state.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-fix-out-of-bounds-access-in-read_block_state.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Longlong Xia <[email protected]>
Subject: zram: fix out-of-bounds access in read_block_state()
Date: Tue, 4 Aug 2026 14:59:19 +0800

read_block_state() calculates nr_pages before taking dev_lock.  If the
device is reset and reinitialized with a smaller disksize before lock
acquisition, nr_pages still describes the old table.  The subsequent loop
can then call slot_lock() past the end of the newly allocated table.

Read disksize after acquiring dev_lock and checking that the device is
initialized.  The read lock then keeps the table and its bound stable for
the duration of the scan.

Link: https://lore.kernel.org/[email protected]
Fixes: c0265342bff4 ("zram: introduce zram memory tracking")
Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Longlong Xia <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 drivers/block/zram/zram_drv.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/block/zram/zram_drv.c~zram-fix-out-of-bounds-access-in-read_block_state
+++ a/drivers/block/zram/zram_drv.c
@@ -1543,7 +1543,7 @@ static ssize_t read_block_state(struct f
 	char *kbuf;
 	ssize_t index, written = 0;
 	struct zram *zram = file->private_data;
-	unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
+	unsigned long nr_pages;
 
 	kbuf = kvmalloc(count, GFP_KERNEL);
 	if (!kbuf)
@@ -1555,6 +1555,8 @@ static ssize_t read_block_state(struct f
 		return -EINVAL;
 	}
 
+	nr_pages = zram->disksize >> PAGE_SHIFT;
+
 	for (index = *ppos; index < nr_pages; index++) {
 		int copied;
 
_

Patches currently in -mm which might be from [email protected] are

mm-ksm-avoid-missing-ksmd-wakeups-in-ksm_enter.patch
zram-fix-out-of-bounds-access-in-writeback_store.patch
zram-fix-out-of-bounds-access-in-read_block_state.patch