On 11/28/2012 05:33 PM, Minchan Kim wrote:
On Wed, Nov 28, 2012 at 02:15:05PM +0900, Minchan Kim wrote:
Hi Nitin,
On Mon, Nov 26, 2012 at 11:26:07PM -0800, Nitin Gupta wrote:
The commit c8f2f0db1 ("zram: Fix handling of incompressible pages")
introduced a bug which caused a kunmap()'ed buffer to be used in case
I got confused by the descripton. :(
The descripton is not right.
The problem is to access freed memory, not accessing to kunmaped buffer.
partial I/O write.
1. uncmem = kmalloc
2. zram_decompress_page(uncmem)
3. memcpy(uncmem, user_mem)
4. lzo1x_1_compress(uncmem)
5. kfree(uncmem)
6. src = uncmem
7. memcpy(cmem, src, clen) <----- HIT
of partial writes where the data was found to be incompressible.
I got it. You shouldn't mention partial write for proper description
because it was usecase for swap-over-zram so it can't make partial write.
Without partial write mention, your description is right but the problem
I mentioned above is another problem for partial write so we need a another
patch. I will cook.
I will include explanation of both the cases: use of unmapped buffer
and freed buffer, when I resend these patches.
This fixes bug 50081:
https://bugzilla.kernel.org/show_bug.cgi?id=50081
Signed-off-by: Nitin Gupta <ngupta@xxxxxxxxxx>
Reported-by: Mihail Kasadjikov <hamer.mk@xxxxxxxxx>
Reported-by: Tomas M <tomas@xxxxxxxx>
Good catch! Shame on me. I should have reivewed more carefully. :(
Please resend it with revised descrption and title.
I will rebase mh patchset just sent on top of this bug fix patch.
P.S) Sigh, Now code isn't clean due to partial read/write path handling.
IMHO, sooner or later, we need refactoring.
--
Kind regards,
Minchan Kim
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