Re: [PATCH -next] jffs2: fix use-after-free in jffs2_clear_xattr_subsystem

[libaokun (A)]

在 2022/3/17 6:01, Richard Weinberger 写道:
> ----- Ursprüngliche Mail -----
> > Von: "libaokun" <libaokun1@xxxxxxxxxx>
> > An: "richard" <richard@xxxxxx>, "David Woodhouse" <dwmw2@xxxxxxxxxxxxx>, "christian brauner"
> > <christian.brauner@xxxxxxxxxx>, "linux-mtd" <linux-mtd@xxxxxxxxxxxxxxxxxxx>, "linux-kernel"
> > <linux-kernel@xxxxxxxxxxxxxxx>
> > CC: "yukuai3" <yukuai3@xxxxxxxxxx>, "stable" <stable@xxxxxxxxxxxxxxx>, "Hulk Robot" <hulkci@xxxxxxxxxx>, "libaokun"
> > <libaokun1@xxxxxxxxxx>
> > Gesendet: Donnerstag, 10. März 2022 09:35:18
> > Betreff: Re: [PATCH -next] jffs2: fix use-after-free in jffs2_clear_xattr_subsystem
> > A gentle ping, sorry for the noise.
> >
> > 在 2021/12/28 20:54, Baokun Li 写道:
> > > When we mount a jffs2 image, assume that the first few blocks of
> > > the image are normal and contain at least one xattr-related inode,
> > > but the next block is abnormal. As a result, an error is returned
> > > in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then
> > > called in jffs2_build_filesystem() and then again in
> > > jffs2_do_fill_super().
> > >
> > > Finally we can observe the following report:
> > >    ==================================================================
> > >    BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac
> > >    Read of size 8 at addr ffff8881243384e0 by task mount/719
> > >
> > >    Call Trace:
> > >     dump_stack+0x115/0x16b
> > >     jffs2_clear_xattr_subsystem+0x95/0x6ac
> > >     jffs2_do_fill_super+0x84f/0xc30
> > >     jffs2_fill_super+0x2ea/0x4c0
> > >     mtd_get_sb+0x254/0x400
> > >     mtd_get_sb_by_nr+0x4f/0xd0
> > >     get_tree_mtd+0x498/0x840
> > >     jffs2_get_tree+0x25/0x30
> > >     vfs_get_tree+0x8d/0x2e0
> > >     path_mount+0x50f/0x1e50
> > >     do_mount+0x107/0x130
> > >     __se_sys_mount+0x1c5/0x2f0
> > >     __x64_sys_mount+0xc7/0x160
> > >     do_syscall_64+0x45/0x70
> > >     entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > >
> > >    Allocated by task 719:
> > >     kasan_save_stack+0x23/0x60
> > >     __kasan_kmalloc.constprop.0+0x10b/0x120
> > >     kasan_slab_alloc+0x12/0x20
> > >     kmem_cache_alloc+0x1c0/0x870
> > >     jffs2_alloc_xattr_ref+0x2f/0xa0
> > >     jffs2_scan_medium.cold+0x3713/0x4794
> > >     jffs2_do_mount_fs.cold+0xa7/0x2253
> > >     jffs2_do_fill_super+0x383/0xc30
> > >     jffs2_fill_super+0x2ea/0x4c0
> > >    [...]
> > >
> > >    Freed by task 719:
> > >     kmem_cache_free+0xcc/0x7b0
> > >     jffs2_free_xattr_ref+0x78/0x98
> > >     jffs2_clear_xattr_subsystem+0xa1/0x6ac
> > >     jffs2_do_mount_fs.cold+0x5e6/0x2253
> > >     jffs2_do_fill_super+0x383/0xc30
> > >     jffs2_fill_super+0x2ea/0x4c0
> > >    [...]
> > >
> > >    The buggy address belongs to the object at ffff8881243384b8
> > >     which belongs to the cache jffs2_xattr_ref of size 48
> > >    The buggy address is located 40 bytes inside of
> > >     48-byte region [ffff8881243384b8, ffff8881243384e8)
> > >    [...]
> > >    ==================================================================
> > >
> > > The triggering of the BUG is shown in the following stack:
> > > -----------------------------------------------------------
> > > jffs2_fill_super
> > >     jffs2_do_fill_super
> > >       jffs2_do_mount_fs
> > >         jffs2_build_filesystem
> > >           jffs2_scan_medium
> > >             jffs2_scan_eraseblock        <--- ERROR
> > >           jffs2_clear_xattr_subsystem    <--- free
> > >       jffs2_clear_xattr_subsystem        <--- free again
> > > -----------------------------------------------------------
> > >
> > > An error is returned in jffs2_do_mount_fs(). If the error is returned
> > > by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to
> > > be executed. If the error is returned by jffs2_build_filesystem(), the
> > > jffs2_clear_xattr_subsystem() also does not need to be executed again.
> > > So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root'
> > > to fix this UAF problem.
> > >
> > > Fixes: aa98d7cf59b5 ("[JFFS2][XATTR] XATTR support on JFFS2 (version. 5)")
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> > > Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
> Applied. Thanks for fixing!
>
> Thanks,
> //richard
> .


Thank you for your review!

--
With Best Regards,
Baokun Li