From 0bc9f5d14a93971c6cd9c0d81b0fc154fc54c65d Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Thu, 28 Mar 2019 20:44:24 -0700 Subject: [PATCH] drivers/block/zram/zram_drv.c: fix idle/writeback string compare Makoto report a below KASAN error: zram does out-of-bounds read. Because strscpy copies from source up to count bytes unconditionally. It could cause out-of-bounds read on next object in slab. To prevent it, use strlcpy which checks source's length automatically. BUG: KASAN: slab-out-of-bounds in strscpy+0x68/0x154 Read of size 8 at addr ffffffc0c3495a00 by task system_server/1314 .. Call trace: strscpy+0x68/0x154 idle_store+0xc4/0x34c dev_attr_store+0x50/0x6c sysfs_kf_write+0x98/0xb4 kernfs_fop_write+0x198/0x260 __vfs_write+0x10c/0x338 vfs_write+0x114/0x238 SyS_write+0xc8/0x168 __sys_trace_return+0x0/0x4 Allocated by task 1314: __kmalloc+0x280/0x318 kernfs_fop_write+0xac/0x260 __vfs_write+0x10c/0x338 vfs_write+0x114/0x238 SyS_write+0xc8/0x168 __sys_trace_return+0x0/0x4 Freed by task 2855: kfree+0x138/0x630 kernfs_put_open_node+0x10c/0x124 kernfs_fop_release+0xd8/0x114 __fput+0x130/0x2a4 ____fput+0x1c/0x28 task_work_run+0x16c/0x1c8 do_notify_resume+0x2bc/0x107c work_pending+0x8/0x10 The buggy address belongs to the object at ffffffc0c3495a00 which belongs to the cache kmalloc-128 of size 128 The buggy address is located 0 bytes inside of 128-byte region [ffffffc0c3495a00, ffffffc0c3495a80) The buggy address belongs to the page: page:ffffffbf030d2500 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 flags: 0x4000000000010200(slab|head) page dumped because: kasan: bad access detected Memory state around the buggy address: ffffffc0c3495900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffffc0c3495980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffffffc0c3495a00: 04 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffffffc0c3495a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffffffc0c3495b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Link: http://lkml.kernel.org/r/20190319231911.145968-1-minchan@kernel.org Cc: [5.0] Signed-off-by: Minchan Kim Reported-by: Makoto Wu Reviewed-by: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/zram/zram_drv.c | 32 ++++++-------------------------- 1 file changed, 6 insertions(+), 26 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index e7a5f1d1c314..399cad7daae7 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -290,18 +290,8 @@ static ssize_t idle_store(struct device *dev, struct zram *zram = dev_to_zram(dev); unsigned long nr_pages = zram->disksize >> PAGE_SHIFT; int index; - char mode_buf[8]; - ssize_t sz; - sz = strscpy(mode_buf, buf, sizeof(mode_buf)); - if (sz <= 0) - return -EINVAL; - - /* ignore trailing new line */ - if (mode_buf[sz - 1] == '\n') - mode_buf[sz - 1] = 0x00; - - if (strcmp(mode_buf, "all")) + if (!sysfs_streq(buf, "all")) return -EINVAL; down_read(&zram->init_lock); @@ -635,25 +625,15 @@ static ssize_t writeback_store(struct device *dev, struct bio bio; struct bio_vec bio_vec; struct page *page; - ssize_t ret, sz; - char mode_buf[8]; - int mode = -1; + ssize_t ret; + int mode; unsigned long blk_idx = 0; - sz = strscpy(mode_buf, buf, sizeof(mode_buf)); - if (sz <= 0) - return -EINVAL; - - /* ignore trailing newline */ - if (mode_buf[sz - 1] == '\n') - mode_buf[sz - 1] = 0x00; - - if (!strcmp(mode_buf, "idle")) + if (sysfs_streq(buf, "idle")) mode = IDLE_WRITEBACK; - else if (!strcmp(mode_buf, "huge")) + else if (sysfs_streq(buf, "huge")) mode = HUGE_WRITEBACK; - - if (mode == -1) + else return -EINVAL; down_read(&zram->init_lock);