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 <[email protected]>
Reported-by: Mihail Kasadjikov <[email protected]>
Reported-by: Tomas M <[email protected]>
---
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
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 <[email protected]>
> Reported-by: Mihail Kasadjikov <[email protected]>
> Reported-by: Tomas M <[email protected]>
> ---
> 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
On Fri, Nov 23, 2012 at 09:17:09AM +0900, Minchan Kim wrote:
> 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?)
Yep. He'll be back on Monday.
regards,
dan carpenter