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authorChristian Brauner <brauner@kernel.org>2023-08-29 18:23:57 +0300
committerChristian Brauner <brauner@kernel.org>2023-08-31 13:47:15 +0300
commitec952aa253c0f49a70d9de7b44b5f5c93e2dfe54 (patch)
tree7b90079309020da73f388c8a8aac97e8316ef922 /drivers/mtd
parent69881be3d9a00cca770886af40913cfc5274b2d0 (diff)
downloadlinux-ec952aa253c0f49a70d9de7b44b5f5c93e2dfe54.tar.xz
mtd: key superblock by device number
The mtd driver has similar problems than the one that was fixed in commit dc3216b14160 ("super: ensure valid info"). The kill_mtd_super() helper calls shuts the superblock down but leaves the superblock on fs_supers as the devices are still in use but puts the mtd device and cleans out the superblock's s_mtd field. This means another mounter can find the superblock on the list accessing its s_mtd field while it is curently in the process of being freed or already freed. Prevent that from happening by keying superblock by dev_t just as we do in the generic code. Link: https://lore.kernel.org/linux-fsdevel/20230829-weitab-lauwarm-49c40fc85863@brauner Acked-by: Richard Weinberger <richard@nod.at> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Message-Id: <20230829-vfs-super-mtd-v1-2-fecb572e5df3@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'drivers/mtd')
-rw-r--r--drivers/mtd/mtdsuper.c45
1 files changed, 11 insertions, 34 deletions
diff --git a/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c
index 5ff001140ef4..b7e3763c47f0 100644
--- a/drivers/mtd/mtdsuper.c
+++ b/drivers/mtd/mtdsuper.c
@@ -20,38 +20,6 @@
#include "mtdcore.h"
/*
- * compare superblocks to see if they're equivalent
- * - they are if the underlying MTD device is the same
- */
-static int mtd_test_super(struct super_block *sb, struct fs_context *fc)
-{
- struct mtd_info *mtd = fc->sget_key;
-
- if (sb->s_mtd == fc->sget_key) {
- pr_debug("MTDSB: Match on device %d (\"%s\")\n",
- mtd->index, mtd->name);
- return 1;
- }
-
- pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n",
- sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
- return 0;
-}
-
-/*
- * mark the superblock by the MTD device it is using
- * - set the device number to be the correct MTD block device for pesuperstence
- * of NFS exports
- */
-static int mtd_set_super(struct super_block *sb, struct fs_context *fc)
-{
- sb->s_mtd = fc->sget_key;
- sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
- sb->s_bdi = bdi_get(mtd_bdi);
- return 0;
-}
-
-/*
* get a superblock on an MTD-backed filesystem
*/
static int mtd_get_sb(struct fs_context *fc,
@@ -62,8 +30,7 @@ static int mtd_get_sb(struct fs_context *fc,
struct super_block *sb;
int ret;
- fc->sget_key = mtd;
- sb = sget_fc(fc, mtd_test_super, mtd_set_super);
+ sb = sget_dev(fc, MKDEV(MTD_BLOCK_MAJOR, mtd->index));
if (IS_ERR(sb))
return PTR_ERR(sb);
@@ -77,6 +44,16 @@ static int mtd_get_sb(struct fs_context *fc,
pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
mtd->index, mtd->name);
+ /*
+ * Would usually have been set with @sb_lock held but in
+ * contrast to sb->s_bdev that's checked with only
+ * @sb_lock held, nothing checks sb->s_mtd without also
+ * holding sb->s_umount and we're holding sb->s_umount
+ * here.
+ */
+ sb->s_mtd = mtd;
+ sb->s_bdi = bdi_get(mtd_bdi);
+
ret = fill_super(sb, fc);
if (ret < 0)
goto error_sb;