Hi Richard,
On 2018/12/20 18:45, Richard Weinberger wrote:
> Am Donnerstag, 20. Dezember 2018, 11:43:08 CET schrieb Hou Tao:
>>
>> On 2018/12/16 0:23, Richard Weinberger wrote:
>>> The rtime compressor assumes that at least two bytes are
>>> compressed.
>>> If we try to compress just one byte, the loop condition will
>>> wrap around and an out-of-bounds write happens.
>>>
>>> Cc: <stable@xxxxxxxxxxxxxxx>
>>> Signed-off-by: Richard Weinberger <richard@xxxxxx>
>>> ---
>>> fs/jffs2/compr_rtime.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>> It seems that it doesn't incur any harm because the minimal allocated
>> size will be 8-bytes and jffs2_rtime_compress() will write 2-bytes into
>> the allocated buffer.
>
> Are you sure about that? I saw odd kernel behavior and KASAN complained too.
>
Sorry for the later reply.
Yes. KASAN complains but it doesn't incur any harm because the minimal allocated
size returned by kmalloc() will be 8-bytes.
But we better fix it, because it's bad to depend on the implementation of kmalloc().
It seems that mtd-utils has already fixed it years ago. Maybe we can use it directly ?
And your fix also looks good to me, so
Reviewed-by: Hou Tao <houtao1@xxxxxxxxxx>
commit e8457f16306ad6e2c8708275bf42b5dfff40fffd
Author: Enrico Scholz <enrico.scholz@xxxxxxxxxxxxxxxxx>
Date: Thu Jun 24 15:02:40 2010 +0200
mkfs.jffs2: fix integer underflow in jffs2_rtime_compress()
When '*dstlen' is 0 or 1, comparison will return wrong result. Reported
by valgrind as
==5919== Invalid write of size 1
==5919== at 0x40564E: jffs2_rtime_compress (compr_rtime.c:51)
==5919== by 0x40676B: jffs2_compress (compr.c:246)
==5919== by 0x403EE4: recursive_populate_directory (mkfs.jffs2.c:884)
==5919== Address 0x4e1bdb1 is 0 bytes after a block of size 1 alloc'd
==5919== at 0x4A0515D: malloc (vg_replace_malloc.c:195)
==5919== by 0x40671C: jffs2_compress (compr.c:229)
==5919== by 0x403EE4: recursive_populate_directory (mkfs.jffs2.c:884)
Signed-off-by: Enrico Scholz <enrico.scholz@xxxxxxxxxxxxxxxxx>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>
diff --git a/compr_rtime.c b/compr_rtime.c
index 131536c..5613963 100644
--- a/compr_rtime.c
+++ b/compr_rtime.c
@@ -32,7 +32,7 @@ static int jffs2_rtime_compress(unsigned char *data_in, unsigned char *cpage_out
memset(positions,0,sizeof(positions));
- while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {
+ while (pos < (*sourcelen) && outpos+2 <= (*dstlen)) {
int backpos, runlen=0;
unsigned char value;
> Thanks,
> //richard
>
>
>
> .
>
