Re: [uml-devel] Hostfs permission checks are all wonky.

[Blaisorblade <blaisorblade@yahoo.it>]

On Monday 28 March 2005 21:48, Rob Landley wrote:
> On Thursday 24 March 2005 05:53 am, Blaisorblade wrote:
> > > You mean like this darn bug I've been seeing for weeks?
> > >
> > > io scheduler noop registered
> > > loop: loaded (max 8 devices)
> > > Initialized stdio console driver
> > > Console initialized on /dev/tty0
> > > VFS: Mounted root (hostfs filesystem).
> > > idr_remove called for id=3 which is not allocated.
> > > Call Trace:
> > > a01fba48:  [<a007cbec>]
> > > a01fba84:  [<a007cc13>]
> > > a01fba9c:  [<a0085eaa>]
> > > a01fbb04:  [<a0085697>]
> > > a01fbb4c:  [<a00860a4>]
> > > a01fbb68:  [<a007d09d>]
> > > a01fbb74:  [<a004cc5e>]
> > > a01fbb7c:  [<a004cdb6>]
> > > a01fbb80:  [<a008e193>]
> > > a01fbba8:  [<a004cd31>]
> > > a01fbbc8:  [<a004526c>]
> > > a01fbbe4:  [<a00451bf>]
> > > a01fbc24:  [<a0045365>]
> > > a01fbc38:  [<a0045445>]
> > > a01fbc54:  [<a0011de9>]
> > > a01fbcc0:  [<a0011e30>]
> > > a01fbce4:  [<a0012d18>]
> > > a01fbd14:  [<a0017887>]
> > > a01fbd20:  [<a0097808>]
> > >
> > > sh-2.05b#
> > >
> > > It does that all the time.  (The id=? bit changes with each run.)
> > > Somewhere around here I've got a trace from when I built it with debug
> > > symbols, I can get that for you at the same time I try out your
> > > patch...
> >
> > I'd like that a lot, and also your .config - I've never seen that message
> > nor I know the users of that kernel internal API (but probably UML itself
> > isn't using that).
>
> VFS: Mounted root (hostfs filesystem).
> idr_remove called for id=1 which is not allocated.
> Call Trace:
> a086fa1c:  [<a00784c2>] sub_remove+0xe0/0xe9
> a086fa58:  [<a00784ea>] idr_remove+0x1f/0x8b
> a086fa74:  [<a007f1d0>] release_dev+0x64f/0x665
> a086fae0:  [<a007e918>] init_dev+0x37e/0x472
> a086fb28:  [<a007f3b7>] tty_open+0x1d1/0x300
> a086fb38:  [<a00789cb>] kobject_get+0x14/0x1c
> a086fb48:  [<a004d6bb>] cdev_get+0xb/0xe
> a086fb54:  [<a004d830>] exact_lock+0xb/0x17
> a086fb5c:  [<a0087911>] kobj_lookup+0x90/0xba
> a086fb6c:  [<a004d81d>] exact_match+0x0/0x8
> a086fb88:  [<a004d79c>] chrdev_open+0xcb/0xe8
> a086fbac:  [<a0045b77>] dentry_open+0xa7/0x151
> a086fbcc:  [<a0045acb>] filp_open+0x40/0x45
> a086fc0c:  [<a0045c76>] get_unused_fd+0x55/0x9d
> a086fc24:  [<a0045d5e>] sys_open+0x32/0x6c
> a086fc44:  [<a0011f57>] execute_syscall_tt+0xd3/0xe0
> a086fcb4:  [<a0011fa2>] syscall_handler_tt+0x3e/0x66
> a086fcdc:  [<a0012e8f>] sig_handler_common_tt+0x93/0xe4
> a086fd10:  [<a0017a48>] sig_handler+0x18/0x27
> a086fd20:  [<a0091728>] __restore+0x0/0x8
While doing other stuff, I've understood how UML reaches that code:

hostfs_read_sb->get_sb_nodev->set_anon_super()->idr_XXX. However, I can't 
understand why the hell UML could have bugs in this path. Probably running it 
with a root hostfs will trigger this, but for now I haven't the time to play 
with this.

Also, I've seen somebody else with a "idr" problem, related to devpts (recent 
posts, titled "ssh again" IIRC). Still I don't understand what's going on.
-- 
Paolo Giarrusso, aka Blaisorblade
Skype user "PaoloGiarrusso"
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade





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