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Date: Fri, 23 Nov 2012 09:17:09 +0900
From: Minchan Kim <minchan@...nel.org>
To: Nitin Gupta <ngupta@...are.org>
Cc: Greg KH <greg@...ah.com>,
Seth Jennings <sjenning@...ux.vnet.ibm.com>,
Dan Carpenter <dan.carpenter@...cle.com>,
Sam Hansen <solid.se7en@...il.com>, Tomas M <tomas@...x.org>,
Mihail Kasadjikov <hamer.mk@...il.com>,
Linux Driver Project <devel@...uxdriverproject.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] staging: zram: Prevent use of unmapped buffer
Hi Nitin,
Current next-20121115(I don't know why linux-next stay at the version. Is there
any problem on the tree? or Stephen go to holiday?) has a 37b51fdd(staging:
zram: factor-out zram_decompress_page() function) so this patch should be based
on that.
Thanks.
On Thu, Nov 22, 2012 at 02:41:13AM -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
> of partial writes where the data was found to be incompressible.
>
> This fixes bug 50081:
> https://bugzilla.kernel.org/show_bug.cgi?id=50081
>
> Signed-off-by: Nitin Gupta <ngupta@...are.org>
> Reported-by: Mihail Kasadjikov <hamer.mk@...il.com>
> Reported-by: Tomas M <tomas@...x.org>
> ---
> drivers/staging/zram/zram_drv.c | 46 +++++++++++++++++++++++++--------------
> 1 file changed, 30 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 6edefde..8d9133f 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -265,8 +265,13 @@ static int zram_read_before_write(struct zram *zram, char *mem, u32 index)
> }
>
> cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
> - ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
> + if (zram->table[index].size == PAGE_SIZE) {
> + memcpy(mem, cmem, PAGE_SIZE);
> + ret = LZO_E_OK;
> + } else {
> + ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
> mem, &clen);
> + }
> zs_unmap_object(zram->mem_pool, handle);
>
> /* Should NEVER happen. Return bio error if it does. */
> @@ -282,7 +287,7 @@ static int zram_read_before_write(struct zram *zram, char *mem, u32 index)
> static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> int offset)
> {
> - int ret;
> + int ret = 0;
> size_t clen;
> unsigned long handle;
> struct page *page;
> @@ -303,10 +308,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> goto out;
> }
> ret = zram_read_before_write(zram, uncmem, index);
> - if (ret) {
> - kfree(uncmem);
> + if (ret)
> goto out;
> - }
> }
>
> /*
> @@ -319,16 +322,18 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>
> user_mem = kmap_atomic(page);
>
> - if (is_partial_io(bvec))
> + if (is_partial_io(bvec)) {
> memcpy(uncmem + offset, user_mem + bvec->bv_offset,
> bvec->bv_len);
> - else
> + kunmap_atomic(user_mem);
> + user_mem = NULL;
> + } else {
> uncmem = user_mem;
> + }
>
> if (page_zero_filled(uncmem)) {
> - kunmap_atomic(user_mem);
> - if (is_partial_io(bvec))
> - kfree(uncmem);
> + if (!is_partial_io(bvec))
> + kunmap_atomic(user_mem);
> zram_stat_inc(&zram->stats.pages_zero);
> zram_set_flag(zram, index, ZRAM_ZERO);
> ret = 0;
> @@ -338,9 +343,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
> zram->compress_workmem);
>
> - kunmap_atomic(user_mem);
> - if (is_partial_io(bvec))
> - kfree(uncmem);
> + if (!is_partial_io(bvec)) {
> + kunmap_atomic(user_mem);
> + user_mem = NULL;
> + uncmem = NULL;
> + }
>
> if (unlikely(ret != LZO_E_OK)) {
> pr_err("Compression failed! err=%d\n", ret);
> @@ -349,8 +356,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>
> if (unlikely(clen > max_zpage_size)) {
> zram_stat_inc(&zram->stats.bad_compress);
> - src = uncmem;
> clen = PAGE_SIZE;
> + src = NULL;
> + if (is_partial_io(bvec))
> + src = uncmem;
> }
>
> handle = zs_malloc(zram->mem_pool, clen);
> @@ -362,7 +371,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> }
> cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
>
> + if ((clen == PAGE_SIZE) && !(is_partial_io(bvec)))
> + src = kmap_atomic(page);
> memcpy(cmem, src, clen);
> + if ((clen == PAGE_SIZE) && !(is_partial_io(bvec)))
> + kunmap_atomic(src);
>
> zs_unmap_object(zram->mem_pool, handle);
>
> @@ -375,9 +388,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> if (clen <= PAGE_SIZE / 2)
> zram_stat_inc(&zram->stats.good_compress);
>
> - return 0;
> -
> out:
> + if (is_partial_io(bvec))
> + kfree(uncmem);
> +
> if (ret)
> zram_stat64_inc(zram, &zram->stats.failed_writes);
> return ret;
> --
> 1.7.10.4
>
> --
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--
Kind regards,
Minchan Kim
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