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Re: Dcache oops

From Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups linux.kernel
Subject Re: Dcache oops
Date 2016-06-03 23:30 +0200
Message-ID <rG4Pf-8ss-11@gated-at.bofh.it> (permalink)
References (4 earlier) <rG0iC-5Cj-25@gated-at.bofh.it> <rG213-6Ka-1@gated-at.bofh.it> <rG2aK-6Nw-1@gated-at.bofh.it> <rG3zP-7MZ-1@gated-at.bofh.it> <rG4Fz-8oJ-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Fri, Jun 03, 2016 at 02:18:15PM -0700, Linus Torvalds wrote:

> So something must have corrupted the qstr.
> 
> The remaining length *should* in %edi, judging by the
> 
>    0xffffffff81243b82 <+306>: cmp    $0x7,%edi
> 
> in the __d_lookup() disassembly. And %rdi contains 2, so there were
> supposed to be two more characters at 'ct' (which is %rdx).

... and since r8 and rsi are 0, we couldn't have consumed anything.
> 
> Why would nd->last.name be bogus? I don't see anything.

An interesting part is that it's page-aligned.  Which is impossible for
a short name obtained by getname(), but is quite likely for a symlink body.
So at a guess, we have a page containing a symlink body freed under us.

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Thread

NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 01:10 +0200
  [PATCH] Allow d_splice_alias to accept hashed dentries green@linuxhacker.ru - 2016-06-03 02:10 +0200
    Re: [PATCH] Allow d_splice_alias to accept hashed dentries Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 02:30 +0200
  Re: NFS/d_splice_alias breakage Trond Myklebust <trondmy@primarydata.com> - 2016-06-03 02:50 +0200
    Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 03:00 +0200
      Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:30 +0200
        Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:40 +0200
    Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:30 +0200
  Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 05:40 +0200
    Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 05:50 +0200
      Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 06:30 +0200
        Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 06:50 +0200
          Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 07:00 +0200
        Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 07:00 +0200
          Re: NFS/d_splice_alias breakage Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 08:00 +0200
            Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-07 01:40 +0200
              Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-10 03:40 +0200
                Re: NFS/d_splice_alias breakage Oleg Drokin <green@linuxhacker.ru> - 2016-06-10 18:50 +0200
        Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 18:40 +0200
          Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 20:30 +0200
            Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 20:40 +0200
              Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 22:10 +0200
                Re: Dcache oops Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-03 23:20 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 23:30 +0200
                Re: Dcache oops Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-04 00:10 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:30 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:30 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:40 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 00:50 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 02:00 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 03:00 +0200
                Re: Dcache oops Jeff Layton <jlayton@poochiereds.net> - 2016-06-04 14:30 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 18:20 +0200
                [PATCH] nfs4: Fix potential use after free of state in nfs4_do_reclaim. green@linuxhacker.ru - 2016-06-04 18:30 +0200
                Re: [PATCH] nfs4: Fix potential use after free of state in  nfs4_do_reclaim. Jeff Layton <jlayton@poochiereds.net> - 2016-06-04 22:00 +0200
                Re: Dcache oops Linus Torvalds <torvalds@linux-foundation.org> - 2016-06-04 00:40 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-04 00:50 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:50 +0200
                Re: Dcache oops Oleg Drokin <green@linuxhacker.ru> - 2016-06-03 23:20 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-03 23:50 +0200
                Re: Dcache oops Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-04 00:20 +0200

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