ubi: fastmap: Fix slab corruption

Booting with UBI fastmap and SLUB debugging enabled results in the
following splats. The problem is that ubi_scan_fastmap() moves the
fastmap blocks from the scan_ai (allocated in scan_fast()) to the ai
allocated in ubi_attach(). This results in two problems:

- When the scan_ai is freed, aebs which were allocated from its slab
cache are still in use.

- When the other ai is being destroyed in destroy_ai(), the
arguments to kmem_cache_free() call are incorrect since aebs on its
->fastmap list were allocated with a slab cache from a differnt ai.

Fix this by making a copy of the aebs in ubi_scan_fastmap() instead of
moving them.

=============================================================================
BUG ubi_aeb_slab_cache (Not tainted): Objects remaining in ubi_aeb_slab_cache on __kmem_cache_shutdown()
-----------------------------------------------------------------------------

INFO: Slab 0xbfd2da3c objects=17 used=1 fp=0xb33d7748 flags=0x40000080
CPU: 1 PID: 118 Comm: ubiattach Tainted: G B 4.9.15 #3
[<80111910>] (unwind_backtrace) from [<8010d498>] (show_stack+0x18/0x1c)
[<8010d498>] (show_stack) from [<804a3274>] (dump_stack+0xb4/0xe0)
[<804a3274>] (dump_stack) from [<8026c47c>] (slab_err+0x78/0x88)
[<8026c47c>] (slab_err) from [<802735bc>] (__kmem_cache_shutdown+0x180/0x3e0)
[<802735bc>] (__kmem_cache_shutdown) from [<8024e13c>] (shutdown_cache+0x1c/0x60)
[<8024e13c>] (shutdown_cache) from [<8024ed64>] (kmem_cache_destroy+0x19c/0x20c)
[<8024ed64>] (kmem_cache_destroy) from [<8057cc14>] (destroy_ai+0x1dc/0x1e8)
[<8057cc14>] (destroy_ai) from [<8057f04c>] (ubi_attach+0x3f4/0x450)
[<8057f04c>] (ubi_attach) from [<8056fe70>] (ubi_attach_mtd_dev+0x60c/0xff8)
[<8056fe70>] (ubi_attach_mtd_dev) from [<80571d78>] (ctrl_cdev_ioctl+0x110/0x2b8)
[<80571d78>] (ctrl_cdev_ioctl) from [<8029c77c>] (do_vfs_ioctl+0xac/0xa00)
[<8029c77c>] (do_vfs_ioctl) from [<8029d10c>] (SyS_ioctl+0x3c/0x64)
[<8029d10c>] (SyS_ioctl) from [<80108860>] (ret_fast_syscall+0x0/0x1c)
INFO: Object 0xb33d7e88 @offset=3720
INFO: Allocated in scan_peb+0x608/0x81c age=72 cpu=1 pid=118
kmem_cache_alloc+0x3b0/0x43c
scan_peb+0x608/0x81c
ubi_attach+0x124/0x450
ubi_attach_mtd_dev+0x60c/0xff8
ctrl_cdev_ioctl+0x110/0x2b8
do_vfs_ioctl+0xac/0xa00
SyS_ioctl+0x3c/0x64
ret_fast_syscall+0x0/0x1c
kmem_cache_destroy ubi_aeb_slab_cache: Slab cache still has objects
CPU: 1 PID: 118 Comm: ubiattach Tainted: G B 4.9.15 #3
[<80111910>] (unwind_backtrace) from [<8010d498>] (show_stack+0x18/0x1c)
[<8010d498>] (show_stack) from [<804a3274>] (dump_stack+0xb4/0xe0)
[<804a3274>] (dump_stack) from [<8024ed80>] (kmem_cache_destroy+0x1b8/0x20c)
[<8024ed80>] (kmem_cache_destroy) from [<8057cc14>] (destroy_ai+0x1dc/0x1e8)
[<8057cc14>] (destroy_ai) from [<8057f04c>] (ubi_attach+0x3f4/0x450)
[<8057f04c>] (ubi_attach) from [<8056fe70>] (ubi_attach_mtd_dev+0x60c/0xff8)
[<8056fe70>] (ubi_attach_mtd_dev) from [<80571d78>] (ctrl_cdev_ioctl+0x110/0x2b8)
[<80571d78>] (ctrl_cdev_ioctl) from [<8029c77c>] (do_vfs_ioctl+0xac/0xa00)
[<8029c77c>] (do_vfs_ioctl) from [<8029d10c>] (SyS_ioctl+0x3c/0x64)
[<8029d10c>] (SyS_ioctl) from [<80108860>] (ret_fast_syscall+0x0/0x1c)
cache_from_obj: Wrong slab cache. ubi_aeb_slab_cache but object is from ubi_aeb_slab_cache
------------[ cut here ]------------
WARNING: CPU: 1 PID: 118 at mm/slab.h:354 kmem_cache_free+0x39c/0x450
Modules linked in:
CPU: 1 PID: 118 Comm: ubiattach Tainted: G B 4.9.15 #3
[<80111910>] (unwind_backtrace) from [<8010d498>] (show_stack+0x18/0x1c)
[<8010d498>] (show_stack) from [<804a3274>] (dump_stack+0xb4/0xe0)
[<804a3274>] (dump_stack) from [<80120e40>] (__warn+0xf4/0x10c)
[<80120e40>] (__warn) from [<80120f20>] (warn_slowpath_null+0x28/0x30)
[<80120f20>] (warn_slowpath_null) from [<80271fe0>] (kmem_cache_free+0x39c/0x450)
[<80271fe0>] (kmem_cache_free) from [<8057cb88>] (destroy_ai+0x150/0x1e8)
[<8057cb88>] (destroy_ai) from [<8057ef1c>] (ubi_attach+0x2c4/0x450)
[<8057ef1c>] (ubi_attach) from [<8056fe70>] (ubi_attach_mtd_dev+0x60c/0xff8)
[<8056fe70>] (ubi_attach_mtd_dev) from [<80571d78>] (ctrl_cdev_ioctl+0x110/0x2b8)
[<80571d78>] (ctrl_cdev_ioctl) from [<8029c77c>] (do_vfs_ioctl+0xac/0xa00)
[<8029c77c>] (do_vfs_ioctl) from [<8029d10c>] (SyS_ioctl+0x3c/0x64)
[<8029d10c>] (SyS_ioctl) from [<80108860>] (ret_fast_syscall+0x0/0x1c)
---[ end trace 2bd8396277fd0a0b ]---
=============================================================================
BUG ubi_aeb_slab_cache (Tainted: G B W ): page slab pointer corrupt.
-----------------------------------------------------------------------------

INFO: Allocated in scan_peb+0x608/0x81c age=104 cpu=1 pid=118
kmem_cache_alloc+0x3b0/0x43c
scan_peb+0x608/0x81c
ubi_attach+0x124/0x450
ubi_attach_mtd_dev+0x60c/0xff8
ctrl_cdev_ioctl+0x110/0x2b8
do_vfs_ioctl+0xac/0xa00
SyS_ioctl+0x3c/0x64
ret_fast_syscall+0x0/0x1c
INFO: Slab 0xbfd2da3c objects=17 used=1 fp=0xb33d7748 flags=0x40000081
INFO: Object 0xb33d7e88 @offset=3720 fp=0xb33d7da0

Redzone b33d7e80: cc cc cc cc cc cc cc cc ........
Object b33d7e88: 02 00 00 00 01 00 00 00 00 f0 ff 7f ff ff ff ff ................
Object b33d7e98: 00 00 00 00 00 00 00 00 bd 16 00 00 00 00 00 00 ................
Object b33d7ea8: 00 01 00 00 00 02 00 00 00 00 00 00 00 00 00 00 ................
Redzone b33d7eb8: cc cc cc cc ....
Padding b33d7f60: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
CPU: 1 PID: 118 Comm: ubiattach Tainted: G B W 4.9.15 #3
[<80111910>] (unwind_backtrace) from [<8010d498>] (show_stack+0x18/0x1c)
[<8010d498>] (show_stack) from [<804a3274>] (dump_stack+0xb4/0xe0)
[<804a3274>] (dump_stack) from [<80271770>] (free_debug_processing+0x320/0x3c4)
[<80271770>] (free_debug_processing) from [<80271ad0>] (__slab_free+0x2bc/0x430)
[<80271ad0>] (__slab_free) from [<80272024>] (kmem_cache_free+0x3e0/0x450)
[<80272024>] (kmem_cache_free) from [<8057cb88>] (destroy_ai+0x150/0x1e8)
[<8057cb88>] (destroy_ai) from [<8057ef1c>] (ubi_attach+0x2c4/0x450)
[<8057ef1c>] (ubi_attach) from [<8056fe70>] (ubi_attach_mtd_dev+0x60c/0xff8)
[<8056fe70>] (ubi_attach_mtd_dev) from [<80571d78>] (ctrl_cdev_ioctl+0x110/0x2b8)
[<80571d78>] (ctrl_cdev_ioctl) from [<8029c77c>] (do_vfs_ioctl+0xac/0xa00)
[<8029c77c>] (do_vfs_ioctl) from [<8029d10c>] (SyS_ioctl+0x3c/0x64)
[<8029d10c>] (SyS_ioctl) from [<80108860>] (ret_fast_syscall+0x0/0x1c)
FIX ubi_aeb_slab_cache: Object at 0xb33d7e88 not freed

Signed-off-by: Rabin Vincent <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

drivers/mtd/ubi/fastmap.c

···
 	return ret;
 }
 
+static struct ubi_ainf_peb *clone_aeb(struct ubi_attach_info *ai,
+				      struct ubi_ainf_peb *old)
+{
+	struct ubi_ainf_peb *new;
+
+	new = ubi_alloc_aeb(ai, old->pnum, old->ec);
+	if (!new)
+		return NULL;
+
+	new->vol_id = old->vol_id;
+	new->sqnum = old->sqnum;
+	new->lnum = old->lnum;
+	new->scrub = old->scrub;
+	new->copy_flag = old->copy_flag;
+
+	return new;
+}
+
 /**
  * ubi_scan_fastmap - scan the fastmap.
  * @ubi: UBI device object
···
 	struct ubi_vid_hdr *vh;
 	struct ubi_ec_hdr *ech;
 	struct ubi_fastmap_layout *fm;
-	struct ubi_ainf_peb *tmp_aeb, *aeb;
+	struct ubi_ainf_peb *aeb;
 	int i, used_blocks, pnum, fm_anchor, ret = 0;
 	size_t fm_size;
 	__be32 crc, tmp_crc;
···
 	if (fm_anchor < 0)
 		return UBI_NO_FASTMAP;
 
-	/* Move all (possible) fastmap blocks into our new attach structure. */
-	list_for_each_entry_safe(aeb, tmp_aeb, &scan_ai->fastmap, u.list)
-		list_move_tail(&aeb->u.list, &ai->fastmap);
+	/* Copy all (possible) fastmap blocks into our new attach structure. */
+	list_for_each_entry(aeb, &scan_ai->fastmap, u.list) {
+		struct ubi_ainf_peb *new;
+
+		new = clone_aeb(ai, aeb);
+		if (!new)
+			return -ENOMEM;
+
+		list_add(&new->u.list, &ai->fastmap);
+	}
 
 	down_write(&ubi->fm_protect);
 	memset(ubi->fm_buf, 0, ubi->fm_size);