Re: [ramfs] 0858d7da8a: canonical_address#:#[##]

From: yangerkun
Date: Thu Nov 25 2021 - 20:57:03 EST


Cc ntfs3:

Maybe it's a problem like this:

do_new_mount
fs_context_for_mount
alloc_fs_context
ntfs_init_fs_context
sbi = kzalloc(sizeof(struct ntfs_sb_info), GFP_NOFS);
fc->s_fs_info = sbi;
vfs_get_tree
ntfs_fs_get_tree
get_tree_bdev
blkdev_get_by_path // return error and sbi->sb will be NULL
put_fs_context
ntfs_fs_free
put_ntfs
ntfs_update_mftmirr
struct super_block *sb = sbi->sb; // NULL
u32 blocksize = sb->s_blocksize; // BOOM

It's actually a ntfs3 bug which may be introduced by:

610f8f5a7baf fs/ntfs3: Use new api for mounting


On 2021/11/26 2:03, Linus Torvalds wrote:
On Thu, Nov 25, 2021 at 6:08 AM kernel test robot <oliver.sang@xxxxxxxxx> wrote:
FYI, we noticed the following commit (built with clang-14):

commit: 0858d7da8a09e440fb192a0239d20249a2d16af8 ("ramfs: fix mount source show for ramfs")

Funky. That commit seems to have nothing to do with the oops:

[ 806.257788][ T204] /dev/root: Can't open blockdev
[ 806.259101][ T204] general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN
[ 806.263082][ T204] KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]

Not a very helpful error message,a nd the KASAN comment makes little sense, but

[ 806.267540][ T204] RIP: 0010:ntfs_update_mftmirr (kbuild/src/consumer/fs/ntfs3/fsntfs.c:834)

That's

u32 blocksize = sb->s_blocksize;

and presumably with KASAN you end up getting hat odd 0xdffffc0000000003 thing.

Anyway, looks like sb is NULL, and the code is

int ntfs_update_mftmirr(struct ntfs_sb_info *sbi, int wait)
{
int err;
struct super_block *sb = sbi->sb;
u32 blocksize = sb->s_blocksize;
sector_t block1, block2;

although I have no idea how sbi->sb could be NULL.

Konstantin? See

https://lore.kernel.org/lkml/20211125140816.GC3109@xsang-OptiPlex-9020/

for the full thing.

Linus
.