linux-kernel - Re: [ramfs] 0858d7da8a: canonical

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Date:   Thu, 25 Nov 2021 10:03:33 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     kernel test robot <oliver.sang@...el.com>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Cc:     yangerkun <yangerkun@...wei.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        kernel test robot <lkp@...el.com>
Subject: Re: [ramfs] 0858d7da8a: canonical_address#:#[##]

On Thu, Nov 25, 2021 at 6:08 AM kernel test robot <oliver.sang@...el.com> 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