diff options
| -rw-r--r-- | fs/compat.c | 12 | ||||
| -rw-r--r-- | fs/read_write.c | 62 | ||||
| -rw-r--r-- | include/linux/fs.h | 1 |
3 files changed, 40 insertions, 35 deletions
diff --git a/fs/compat.c b/fs/compat.c index 52cfeb6..ff66c0d 100644 --- a/fs/compat.c +++ b/fs/compat.c @@ -606,14 +606,14 @@ ssize_t compat_rw_copy_check_uvector(int type, /* * Single unix specification: * We should -EINVAL if an element length is not >= 0 and fitting an - * ssize_t. The total length is fitting an ssize_t + * ssize_t. * - * Be careful here because iov_len is a size_t not an ssize_t + * In Linux, the total length is limited to MAX_RW_COUNT, there is + * no overflow possibility. */ tot_len = 0; ret = -EINVAL; for (seg = 0; seg < nr_segs; seg++) { - compat_ssize_t tmp = tot_len; compat_uptr_t buf; compat_ssize_t len; @@ -624,13 +624,13 @@ ssize_t compat_rw_copy_check_uvector(int type, } if (len < 0) /* size_t not fitting in compat_ssize_t .. */ goto out; - tot_len += len; - if (tot_len < tmp) /* maths overflow on the compat_ssize_t */ - goto out; if (!access_ok(vrfy_dir(type), compat_ptr(buf), len)) { ret = -EFAULT; goto out; } + if (len > MAX_RW_COUNT - tot_len) + len = MAX_RW_COUNT - tot_len; + tot_len += len; iov->iov_base = compat_ptr(buf); iov->iov_len = (compat_size_t) len; uvector++; diff --git a/fs/read_write.c b/fs/read_write.c index 9cd9d14..431a0ed 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -243,8 +243,6 @@ bad: * them to something that fits in "int" so that others * won't have to do range checks all the time. */ -#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK) - int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count) { struct inode *inode; @@ -584,65 +582,71 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector, unsigned long nr_segs, unsigned long fast_segs, struct iovec *fast_pointer, struct iovec **ret_pointer) - { +{ unsigned long seg; - ssize_t ret; + ssize_t ret; struct iovec *iov = fast_pointer; - /* - * SuS says "The readv() function *may* fail if the iovcnt argument - * was less than or equal to 0, or greater than {IOV_MAX}. Linux has - * traditionally returned zero for zero segments, so... - */ + /* + * SuS says "The readv() function *may* fail if the iovcnt argument + * was less than or equal to 0, or greater than {IOV_MAX}. Linux has + * traditionally returned zero for zero segments, so... + */ if (nr_segs == 0) { ret = 0; - goto out; + goto out; } - /* - * First get the "struct iovec" from user memory and - * verify all the pointers - */ + /* + * First get the "struct iovec" from user memory and + * verify all the pointers + */ if (nr_segs > UIO_MAXIOV) { ret = -EINVAL; - goto out; + goto out; } if (nr_segs > fast_segs) { - iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL); + iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL); if (iov == NULL) { ret = -ENOMEM; - goto out; + goto out; } - } + } if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) { ret = -EFAULT; - goto out; + goto out; } - /* + /* * According to the Single Unix Specification we should return EINVAL * if an element length is < 0 when cast to ssize_t or if the * total length would overflow the ssize_t return value of the * system call. - */ + * + * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the + * overflow case. + */ ret = 0; - for (seg = 0; seg < nr_segs; seg++) { - void __user *buf = iov[seg].iov_base; - ssize_t len = (ssize_t)iov[seg].iov_len; + for (seg = 0; seg < nr_segs; seg++) { + void __user *buf = iov[seg].iov_base; + ssize_t len = (ssize_t)iov[seg].iov_len; /* see if we we're about to use an invalid len or if * it's about to overflow ssize_t */ - if (len < 0 || (ret + len < ret)) { + if (len < 0) { ret = -EINVAL; - goto out; + goto out; } if (unlikely(!access_ok(vrfy_dir(type), buf, len))) { ret = -EFAULT; - goto out; + goto out; + } + if (len > MAX_RW_COUNT - ret) { + len = MAX_RW_COUNT - ret; + iov[seg].iov_len = len; } - ret += len; - } + } out: *ret_pointer = iov; return ret; diff --git a/include/linux/fs.h b/include/linux/fs.h index 4d07902..7b7b507 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1867,6 +1867,7 @@ extern int current_umask(void); /* /sys/fs */ extern struct kobject *fs_kobj; +#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK) extern int rw_verify_area(int, struct file *, loff_t *, size_t); #define FLOCK_VERIFY_READ 1 |