target/linux/generic/hack-5.10/401-mtd-super-don-t-reply-on-mtdblock-device-minor.patch

   1 From f9760b158f610b1792a222cc924073724c061bfb Mon Sep 17 00:00:00 2001
   2 From: Daniel Golle <daniel@makrotopia.org>
   3 Date: Wed, 7 Apr 2021 22:37:57 +0100
   4 Subject: [PATCH 1/2] mtd: super: don't reply on mtdblock device minor
   5 To: linux-mtd@lists.infradead.org
   6 Cc: Vignesh Raghavendra <vigneshr@ti.com>,
   7     Richard Weinberger <richard@nod.at>,
   8     Miquel Raynal <miquel.raynal@bootlin.com>,
   9     David Woodhouse <dwmw2@infradead.org>
  10
  11 For blktrans devices with partitions (ie. part_bits != 0) the
  12 assumption that the minor number of the mtdblock device matches
  13 the mtdnum doesn't hold true.
  14 Properly resolve mtd device from blktrans layer instead.
  15
  16 Signed-off-by: Daniel Golle <daniel@makrotopia.org>
  17 ---
  18  drivers/mtd/mtdsuper.c | 33 ++++++++++++++++++++++++++-------
  19  1 file changed, 26 insertions(+), 7 deletions(-)
  20
  21 --- a/drivers/mtd/mtdsuper.c
  22 +++ b/drivers/mtd/mtdsuper.c
  23 @@ -9,6 +9,7 @@
  24   */
  25
  26  #include <linux/mtd/super.h>
  27 +#include <linux/mtd/blktrans.h>
  28  #include <linux/namei.h>
  29  #include <linux/export.h>
  30  #include <linux/ctype.h>
  31 @@ -121,7 +122,8 @@ int get_tree_mtd(struct fs_context *fc,
  32  {
  33  #ifdef CONFIG_BLOCK
  34         struct block_device *bdev;
  35 -       int ret, major;
  36 +       struct mtd_blktrans_dev *blktrans_dev;
  37 +       int ret, major, part_bits;
  38  #endif
  39         int mtdnr;
  40
  41 @@ -169,21 +171,38 @@ int get_tree_mtd(struct fs_context *fc,
  42         /* try the old way - the hack where we allowed users to mount
  43          * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
  44          */
  45 -       bdev = lookup_bdev(fc->source);
  46 +       bdev = blkdev_get_by_path(fc->source, FMODE_READ, NULL);
  47         if (IS_ERR(bdev)) {
  48                 ret = PTR_ERR(bdev);
  49                 errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret);
  50                 return ret;
  51         }
  52 -       pr_debug("MTDSB: lookup_bdev() returned 0\n");
  53 +       pr_debug("MTDSB: blkdev_get_by_path() returned 0\n");
  54
  55         major = MAJOR(bdev->bd_dev);
  56 -       mtdnr = MINOR(bdev->bd_dev);
  57 -       bdput(bdev);
  58
  59 -       if (major == MTD_BLOCK_MAJOR)
  60 -               return mtd_get_sb_by_nr(fc, mtdnr, fill_super);
  61 +       if (major == MTD_BLOCK_MAJOR) {
  62 +               if (!bdev->bd_disk) {
  63 +                       blkdev_put(bdev, FMODE_READ);
  64 +                       BUG();
  65 +                       return -EINVAL;
  66 +               }
  67 +
  68 +               blktrans_dev = (struct mtd_blktrans_dev *)(bdev->bd_disk->private_data);
  69 +               if (!blktrans_dev || !blktrans_dev->tr) {
  70 +                       blkdev_put(bdev, FMODE_READ);
  71 +                       BUG();
  72 +                       return -EINVAL;
  73 +               }
  74 +               mtdnr = blktrans_dev->devnum;
  75 +               part_bits = blktrans_dev->tr->part_bits;
  76 +               blkdev_put(bdev, FMODE_READ);
  77 +               if (MINOR(bdev->bd_dev) != (mtdnr << part_bits))
  78 +                       return -EINVAL;
  79
  80 +               return mtd_get_sb_by_nr(fc, mtdnr, fill_super);
  81 +       }
  82 +       blkdev_put(bdev, FMODE_READ);
  83  #endif /* CONFIG_BLOCK */
  84
  85         if (!(fc->sb_flags & SB_SILENT))