Patch "ubi: Fix use-after-free when volume resizing failed" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ubi: Fix use-after-free when volume resizing failed

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ubi-fix-use-after-free-when-volume-resizing-failed.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 491993dee82ef685ad3846ff66594e623d680258
Author: Li Zetao <lizetao1@xxxxxxxxxx>
Date:   Fri Oct 21 18:21:56 2022 +0800

    ubi: Fix use-after-free when volume resizing failed
    
    [ Upstream commit 9af31d6ec1a4be4caab2550096c6bd2ba8fba472 ]
    
    There is an use-after-free problem reported by KASAN:
      ==================================================================
      BUG: KASAN: use-after-free in ubi_eba_copy_table+0x11f/0x1c0 [ubi]
      Read of size 8 at addr ffff888101eec008 by task ubirsvol/4735
    
      CPU: 2 PID: 4735 Comm: ubirsvol
      Not tainted 6.1.0-rc1-00003-g84fa3304a7fc-dirty #14
      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
      BIOS 1.14.0-1.fc33 04/01/2014
      Call Trace:
       <TASK>
       dump_stack_lvl+0x34/0x44
       print_report+0x171/0x472
       kasan_report+0xad/0x130
       ubi_eba_copy_table+0x11f/0x1c0 [ubi]
       ubi_resize_volume+0x4f9/0xbc0 [ubi]
       ubi_cdev_ioctl+0x701/0x1850 [ubi]
       __x64_sys_ioctl+0x11d/0x170
       do_syscall_64+0x35/0x80
       entry_SYSCALL_64_after_hwframe+0x46/0xb0
       </TASK>
    
    When ubi_change_vtbl_record() returns an error in ubi_resize_volume(),
    "new_eba_tbl" will be freed on error handing path, but it is holded
    by "vol->eba_tbl" in ubi_eba_replace_table(). It means that the liftcycle
    of "vol->eba_tbl" and "vol" are different, so when resizing volume in
    next time, it causing an use-after-free fault.
    
    Fix it by not freeing "new_eba_tbl" after it replaced in
    ubi_eba_replace_table(), while will be freed in next volume resizing.
    
    Fixes: 801c135ce73d ("UBI: Unsorted Block Images")
    Signed-off-by: Li Zetao <lizetao1@xxxxxxxxxx>
    Reviewed-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
    Signed-off-by: Richard Weinberger <richard@xxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 9f6ffd340a3ef..525aa795f934d 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -477,7 +477,7 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
 		for (i = 0; i < -pebs; i++) {
 			err = ubi_eba_unmap_leb(ubi, vol, reserved_pebs + i);
 			if (err)
-				goto out_acc;
+				goto out_free;
 		}
 		spin_lock(&ubi->volumes_lock);
 		ubi->rsvd_pebs += pebs;
@@ -525,6 +525,8 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
 		ubi->avail_pebs += pebs;
 		spin_unlock(&ubi->volumes_lock);
 	}
+	return err;
+
 out_free:
 	kfree(new_eba_tbl);
 	return err;