Messages in this thread | | | Date | Mon, 29 Oct 2012 21:57:08 +0300 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH 1/2] zram: factor-out zram_decompress_page() function (v2) |
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On (10/29/12 11:32), Nitin Gupta wrote: > > Nothing should be printed (even a debug only message) for > the ZRAM_ZERO case. This case can be quite common for certain > kinds of data and would cause a huge log spew. Also (!handle) case > is not the same as zero-filled page case, so this message would > be misleading. > > So, we should either get rid of this warning entirely or only do > pr_debug("Read before write ....") for (!handle) case and log nothing > for ZRAM_ZERO case. >
I'd rather remove this message. Will resend.
By the way, about use after-free. I'm afraid you fix is not covering 100% of the cases.
The problem is with this case: [..] 334 335 if (unlikely(clen > max_zpage_size)) { 336 zram_stat_inc(&zram->stats.bad_compress); 337 src = uncmem; 338 clen = PAGE_SIZE; 339 } 340 [..]
where uncmem could be: -- kmap'ed page -- kmalloc'ed page
both of which were unmap'ed/kfree'd before. you moved kfree to the end of the function, while kunmap_atomic(user_mem) is still happening before src = uncmem/memcpy(cmem, src, clen) pair.
-ss
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