[PATCH 2/2] zram: fix out-of-bounds access in read_block_state()
Longlong Xia <[email protected]>
| Newsgroups | gmane.linux.block,gmane.linux.kernel,gmane.linux.kernel.stable |
|---|---|
| Message-ID | <[email protected]> |
From: Longlong Xia <[email protected]> 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. Fixes: c0265342bff4 ("zram: introduce zram memory tracking") Cc: <[email protected]> Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Longlong Xia <[email protected]> --- drivers/block/zram/zram_drv.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 02fd64475a9a..e5f42f56220d 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1552,7 +1552,7 @@ static ssize_t read_block_state(struct file *file, char __user *buf, 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) @@ -1564,6 +1564,8 @@ static ssize_t read_block_state(struct file *file, char __user *buf, return -EINVAL; } + nr_pages = zram->disksize >> PAGE_SHIFT; + for (index = *ppos; index < nr_pages; index++) { int copied; -- 2.43.0