Messages in this thread | | | Date | Wed, 28 Nov 2012 17:45:24 -0800 | From | Nitin Gupta <> | Subject | Re: [PATCH] zram: Prevent use of unmapped buffer |
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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@vflare.org> >>> Reported-by: Mihail Kasadjikov <hamer.mk@gmail.com> >>> Reported-by: Tomas M <tomas@slax.org> >> 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 >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/
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