diff options
Diffstat (limited to 'mm/filemap.h')
| -rw-r--r-- | mm/filemap.h | 36 |
1 files changed, 23 insertions, 13 deletions
diff --git a/mm/filemap.h b/mm/filemap.h index 13793ba0ce1..3f2a343c601 100644 --- a/mm/filemap.h +++ b/mm/filemap.h @@ -13,18 +13,26 @@ #include <linux/highmem.h> #include <linux/uio.h> #include <linux/config.h> -#include <asm/uaccess.h> +#include <linux/uaccess.h> size_t -__filemap_copy_from_user_iovec(char *vaddr, - const struct iovec *iov, - size_t base, - size_t bytes); +__filemap_copy_from_user_iovec_inatomic(char *vaddr, + const struct iovec *iov, + size_t base, + size_t bytes); /* * Copy as much as we can into the page and return the number of bytes which * were sucessfully copied. If a fault is encountered then clear the page * out to (offset+bytes) and return the number of bytes which were copied. + * + * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache + * to *NOT* zero any tail of the buffer that it failed to copy. If it does, + * and if the following non-atomic copy succeeds, then there is a small window + * where the target page contains neither the data before the write, nor the + * data after the write (it contains zero). A read at this time will see + * data that is inconsistent with any ordering of the read and the write. + * (This has been detected in practice). */ static inline size_t filemap_copy_from_user(struct page *page, unsigned long offset, @@ -34,13 +42,13 @@ filemap_copy_from_user(struct page *page, unsigned long offset, int left; kaddr = kmap_atomic(page, KM_USER0); - left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); + left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes); kunmap_atomic(kaddr, KM_USER0); if (left != 0) { /* Do it the slow way */ kaddr = kmap(page); - left = __copy_from_user(kaddr + offset, buf, bytes); + left = __copy_from_user_nocache(kaddr + offset, buf, bytes); kunmap(page); } return bytes - left; @@ -60,13 +68,15 @@ filemap_copy_from_user_iovec(struct page *page, unsigned long offset, size_t copied; kaddr = kmap_atomic(page, KM_USER0); - copied = __filemap_copy_from_user_iovec(kaddr + offset, iov, - base, bytes); + copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov, + base, bytes); kunmap_atomic(kaddr, KM_USER0); if (copied != bytes) { kaddr = kmap(page); - copied = __filemap_copy_from_user_iovec(kaddr + offset, iov, - base, bytes); + copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov, + base, bytes); + if (bytes - copied) + memset(kaddr + offset + copied, 0, bytes - copied); kunmap(page); } return copied; @@ -78,7 +88,7 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes) const struct iovec *iov = *iovp; size_t base = *basep; - while (bytes) { + do { int copy = min(bytes, iov->iov_len - base); bytes -= copy; @@ -87,7 +97,7 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes) iov++; base = 0; } - } + } while (bytes); *iovp = iov; *basep = base; } |