linux-kernel - Re: [PATCH] jffs2: check the validity of dstlen in jffs2_zlib

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Message-ID: <b7d9d9db42d639aa143f6e6b98ca7b9f4dcfd46e.camel@infinera.com>
Date:   Thu, 28 Jan 2021 11:17:34 +0000
From:   Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
To:     "menglong8.dong@...il.com" <menglong8.dong@...il.com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>
CC:     "yang.yang29@....com.cn" <yang.yang29@....com.cn>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "richard@....at" <richard@....at>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH] jffs2: check the validity of dstlen in
 jffs2_zlib_compress()

On Thu, 2021-01-28 at 02:55 -0800, menglong8.dong@...il.com wrote:
> From: Yang Yang <yang.yang29@....com.cn>
> 
> KASAN reports a BUG when download file in jffs2 filesystem.It is
> because when dstlen == 1, cpage_out will write array out of bounds.
> Actually, data will not be compressed in jffs2_zlib_compress() if
> data's length less than 4.

Ouch, data corruption will ensue. Good find!
I think this needs to go to stable as well.

 Jocke

> 
> [  393.799778] BUG: KASAN: slab-out-of-bounds in jffs2_rtime_compress+0x214/0x2f0 at addr ffff800062e3b281
> [  393.809166] Write of size 1 by task tftp/2918
> [  393.813526] CPU: 3 PID: 2918 Comm: tftp Tainted: G    B           4.9.115-rt93-EMBSYS-CGEL-6.1.R6-dirty #1
> [  393.823173] Hardware name: LS1043A RDB Board (DT)
> [  393.827870] Call trace:
> [  393.830322] [<ffff20000808c700>] dump_backtrace+0x0/0x2f0
> [  393.835721] [<ffff20000808ca04>] show_stack+0x14/0x20
> [  393.840774] [<ffff2000086ef700>] dump_stack+0x90/0xb0
> [  393.845829] [<ffff20000827b19c>] kasan_object_err+0x24/0x80
> [  393.851402] [<ffff20000827b404>] kasan_report_error+0x1b4/0x4d8
> [  393.857323] [<ffff20000827bae8>] kasan_report+0x38/0x40
> [  393.862548] [<ffff200008279d44>] __asan_store1+0x4c/0x58
> [  393.867859] [<ffff2000084ce2ec>] jffs2_rtime_compress+0x214/0x2f0
> [  393.873955] [<ffff2000084bb3b0>] jffs2_selected_compress+0x178/0x2a0
> [  393.880308] [<ffff2000084bb530>] jffs2_compress+0x58/0x478
> [  393.885796] [<ffff2000084c5b34>] jffs2_write_inode_range+0x13c/0x450
> [  393.892150] [<ffff2000084be0b8>] jffs2_write_end+0x2a8/0x4a0
> [  393.897811] [<ffff2000081f3008>] generic_perform_write+0x1c0/0x280
> [  393.903990] [<ffff2000081f5074>] __generic_file_write_iter+0x1c4/0x228
> [  393.910517] [<ffff2000081f5210>] generic_file_write_iter+0x138/0x288
> [  393.916870] [<ffff20000829ec1c>] __vfs_write+0x1b4/0x238
> [  393.922181] [<ffff20000829ff00>] vfs_write+0xd0/0x238
> [  393.927232] [<ffff2000082a1ba8>] SyS_write+0xa0/0x110
> [  393.932283] [<ffff20000808429c>] __sys_trace_return+0x0/0x4
> [  393.937851] Object at ffff800062e3b280, in cache kmalloc-64 size: 64
> [  393.944197] Allocated:
> [  393.946552] PID = 2918
> [  393.948913]  save_stack_trace_tsk+0x0/0x220
> [  393.953096]  save_stack_trace+0x18/0x20
> [  393.956932]  kasan_kmalloc+0xd8/0x188
> [  393.960594]  __kmalloc+0x144/0x238
> [  393.963994]  jffs2_selected_compress+0x48/0x2a0
> [  393.968524]  jffs2_compress+0x58/0x478
> [  393.972273]  jffs2_write_inode_range+0x13c/0x450
> [  393.976889]  jffs2_write_end+0x2a8/0x4a0
> [  393.980810]  generic_perform_write+0x1c0/0x280
> [  393.985251]  __generic_file_write_iter+0x1c4/0x228
> [  393.990040]  generic_file_write_iter+0x138/0x288
> [  393.994655]  __vfs_write+0x1b4/0x238
> [  393.998228]  vfs_write+0xd0/0x238
> [  394.001543]  SyS_write+0xa0/0x110
> [  394.004856]  __sys_trace_return+0x0/0x4
> [  394.008684] Freed:
> [  394.010691] PID = 2918
> [  394.013051]  save_stack_trace_tsk+0x0/0x220
> [  394.017233]  save_stack_trace+0x18/0x20
> [  394.021069]  kasan_slab_free+0x88/0x188
> [  394.024902]  kfree+0x6c/0x1d8
> [  394.027868]  jffs2_sum_write_sumnode+0x2c4/0x880
> [  394.032486]  jffs2_do_reserve_space+0x198/0x598
> [  394.037016]  jffs2_reserve_space+0x3f8/0x4d8
> [  394.041286]  jffs2_write_inode_range+0xf0/0x450
> [  394.045816]  jffs2_write_end+0x2a8/0x4a0
> [  394.049737]  generic_perform_write+0x1c0/0x280
> [  394.054179]  __generic_file_write_iter+0x1c4/0x228
> [  394.058968]  generic_file_write_iter+0x138/0x288
> [  394.063583]  __vfs_write+0x1b4/0x238
> [  394.067157]  vfs_write+0xd0/0x238
> [  394.070470]  SyS_write+0xa0/0x110
> [  394.073783]  __sys_trace_return+0x0/0x4
> [  394.077612] Memory state around the buggy address:
> [  394.082404]  ffff800062e3b180: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> [  394.089623]  ffff800062e3b200: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> [  394.096842] >ffff800062e3b280: 01 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [  394.104056]                    ^
> [  394.107283]  ffff800062e3b300: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> [  394.114502]  ffff800062e3b380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> [  394.121718] ==================================================================
> 
> Signed-off-by: Yang Yang <yang.yang29@....com.cn>
> ---
>  fs/jffs2/compr_rtime.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/jffs2/compr_rtime.c b/fs/jffs2/compr_rtime.c
> index 406d9cc84ba8..79e771ab624f 100644
> --- a/fs/jffs2/compr_rtime.c
> +++ b/fs/jffs2/compr_rtime.c
> @@ -37,6 +37,9 @@ static int jffs2_rtime_compress(unsigned char *data_in,
>  	int outpos = 0;
>  	int pos=0;
>  
> 
> 
> 
> +	if (*dstlen <= 3)
> +		return -1;
> +
>  	memset(positions,0,sizeof(positions));
>  
> 
> 
> 
>  	while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {