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Date: Tue, 29 Mar 2016 23:14:27 +0200
From: Yves-Alexis Perez <corsac@...ian.org>
To: oss-security@...ts.openwall.com, Theodore Tso <tytso@...gle.com>, 
	linux-ext4@...r.kernel.org
Subject: Re: CVE Request - Linux kernel (multiple versions)
 ext2/ext3  filesystem DoS

[dropping MITRE from CC since it's not about the CVE]
[adding ext and Theodore to CC]

On mar., 2016-03-29 at 19:24 +0200, Hugues ANGUELKOV wrote:
> Hello,
> 
> The linux kernel is prone to a Denial of service when mounting specially
> crafted ext2/ext3 (possibly ext4) filesystems. This occurs in the function
> ext4_handle_error who call the panic function on precise circumstance.

Did you contact the upstream maintainers about this? I'm adding them just in
case they're not already aware of that…

> This was tested on severals linux kernel version: 3.10, 3.18, 3.19, on
> real hardware and Xen DomU PV & HVM (the crash report attached is from a
> Fedora 3.18 PV DomU), from different distribution release: Ubuntu, CentOS,
> Fedora, Linux Mint, QubesOS.
> This a low security impact bug, because generally only root can mount
> image, however on Desktop (or possibly server?) system configured with
> automount the bug is easily triggable (think of android smartphone?Haven't
> test yet).
> The crafted image may be burn onto SD card or USB key to crash a large
> panel of linux box.
> 
> 
> [ 929.200197] EXT4-fs error (device loop0): ext4_iget:4058: inode #2: comm
> mount: bad extended attribute block 8390656
> [ 929.200226] Kernel panic - not syncing: EXT4-fs (device loop0): panic
> forced after error
> [ 929.200226]
> [ 929.200230] CPU: 1 PID: 980 Comm: mount Tainted: G O
> 3.18.17-8.pvops.qubes.x86_64 #1
> [ 929.200233] 0000000000000000 000000007533690c ffff88000ea07aa8
> ffffffff81722191
> [ 929.200237] 0000000000000000 ffffffff81a84108 ffff88000ea07b28
> ffffffff8171a462
> [ 929.200240] ffff880000000010 ffff88000ea07b38 ffff88000ea07ad8
> 000000007533690c
> [ 929.200244] Call Trace:
> [ 929.200249] [<ffffffff81722191>] dump_stack+0x46/0x58
> [ 929.200253] [<ffffffff8171a462>] panic+0xd0/0x204
> [ 929.200257] [<ffffffff812ae4d6>] ext4_handle_error.part.188+0x96/0xa0
> [ 929.200260] [<ffffffff812ae838>] __ext4_error_inode+0xa8/0x180
> [ 929.200264] [<ffffffff81292869>] ext4_iget+0x929/0xae0
> [ 929.200267] [<ffffffff812b31fb>] ext4_fill_super+0x18db/0x2b60
> [ 929.200270] [<ffffffff8120af20>] mount_bdev+0x1b0/0x1f0
> [ 929.200273] [<ffffffff812b1920>] ? ext4_calculate_overhead+0x3d0/0x3d0
> [ 929.200276] [<ffffffff812a3425>] ext4_mount+0x15/0x20
> [ 929.200278] [<ffffffff8120b879>] mount_fs+0x39/0x1b0
> [ 929.200282] [<ffffffff811afd95>] ? __alloc_percpu+0x15/0x20
> [ 929.200285] [<ffffffff8122754b>] vfs_kern_mount+0x6b/0x110
> [ 929.200287] [<ffffffff8122a38c>] do_mount+0x22c/0xb60
> [ 929.200290] [<ffffffff811aab96>] ? memdup_user+0x46/0x80
> [ 929.200292] [<ffffffff8122b002>] SyS_mount+0xa2/0x110
> [ 929.200295] [<ffffffff8172a609>] system_call_fastpath+0x12/0x17
> [ 929.200301] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation
> range: 0xffffffff80000000-0xffffffff9fffffff)c
> 
> I cannot attach the PoC (2x2MB too large) nor sending it in plain text
> (they are filesystems), so I've uploaded it on this website of free file
> sharing ... (sorry for the inconvenient):
> poc.ext2 https://1fichier.com/?zbk2gohk8s
> poc.ext3 https://1fichier.com/?9r0c8agjfa
> 
> Can you assign a CVE for this?
> Thank for reading and your time.
> 
> Hugues ANGUELKOV.
> 
> 
-- 
Yves-Alexis


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