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| author | Tejun Heo <htejun@gmail.com> | 2007-11-27 09:30:39 +0100 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2007-11-27 09:30:39 +0100 |
| commit | 645a8d94629fd812a220d54876339a1ddafd9bc2 (patch) | |
| tree | ea333b0ae1dd478e8a902a3bab780a1c6d673304 /include | |
| parent | 7c9f29b128aab5ac95af553e8d8e0e372647f1d5 (diff) | |
| download | lwn-645a8d94629fd812a220d54876339a1ddafd9bc2.tar.gz lwn-645a8d94629fd812a220d54876339a1ddafd9bc2.zip | |
scatterlist: add more safeguards
Add more safeguards to protect against misinterpreting a chain entry
as a normal scatterlist and vice-versa.
* Make sure the entry isn't a chain when assigning and reading a
normal sg.
* Clear offset and length when chaining.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/scatterlist.h | 37 |
1 files changed, 26 insertions, 11 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 259735044148..416e000dfe81 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -26,6 +26,16 @@ #define SG_MAGIC 0x87654321 +/* + * We overload the LSB of the page pointer to indicate whether it's + * a valid sg entry, or whether it points to the start of a new scatterlist. + * Those low bits are there for everyone! (thanks mason :-) + */ +#define sg_is_chain(sg) ((sg)->page_link & 0x01) +#define sg_is_last(sg) ((sg)->page_link & 0x02) +#define sg_chain_ptr(sg) \ + ((struct scatterlist *) ((sg)->page_link & ~0x03)) + /** * sg_assign_page - Assign a given page to an SG entry * @sg: SG entry @@ -47,6 +57,7 @@ static inline void sg_assign_page(struct scatterlist *sg, struct page *page) BUG_ON((unsigned long) page & 0x03); #ifdef CONFIG_DEBUG_SG BUG_ON(sg->sg_magic != SG_MAGIC); + BUG_ON(sg_is_chain(sg)); #endif sg->page_link = page_link | (unsigned long) page; } @@ -73,7 +84,14 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page, sg->length = len; } -#define sg_page(sg) ((struct page *) ((sg)->page_link & ~0x3)) +static inline struct page *sg_page(struct scatterlist *sg) +{ +#ifdef CONFIG_DEBUG_SG + BUG_ON(sg->sg_magic != SG_MAGIC); + BUG_ON(sg_is_chain(sg)); +#endif + return (struct page *)((sg)->page_link & ~0x3); +} /** * sg_set_buf - Set sg entry to point at given data @@ -88,16 +106,6 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf, sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf)); } -/* - * We overload the LSB of the page pointer to indicate whether it's - * a valid sg entry, or whether it points to the start of a new scatterlist. - * Those low bits are there for everyone! (thanks mason :-) - */ -#define sg_is_chain(sg) ((sg)->page_link & 0x01) -#define sg_is_last(sg) ((sg)->page_link & 0x02) -#define sg_chain_ptr(sg) \ - ((struct scatterlist *) ((sg)->page_link & ~0x03)) - /** * sg_next - return the next scatterlist entry in a list * @sg: The current sg entry @@ -179,6 +187,13 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, #ifndef ARCH_HAS_SG_CHAIN BUG(); #endif + + /* + * offset and length are unused for chain entry. Clear them. + */ + prv->offset = 0; + prv->length = 0; + /* * Set lowest bit to indicate a link pointer, and make sure to clear * the termination bit if it happens to be set. |