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random: fix seeding with zero entropy 

Add data from zero-entropy random_writes directly to output pools to
avoid accounting difficulties on machines without entropy sources.

Tested on lguest with all entropy sources disabled.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matt Mackall 2007-05-29 21:58:10 -05:00 committed by Linus Torvalds
parent 602b6aeefe
commit 7f397dcdb7
1 changed files with 34 additions and 27 deletions
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61
drivers/char/random.c
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@ -1020,37 +1020,44 @@ random_poll(struct file *file, poll_table * wait)
return mask;
}
static int
write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
{
size_t bytes;
__u32 buf[16];
const char __user *p = buffer;
while (count > 0) {
bytes = min(count, sizeof(buf));
if (copy_from_user(&buf, p, bytes))
return -EFAULT;
count -= bytes;
p += bytes;
add_entropy_words(r, buf, (bytes + 3) / 4);
}
return 0;
}
static ssize_t
random_write(struct file * file, const char __user * buffer,
size_t count, loff_t *ppos)
{
int ret = 0;
size_t bytes;
__u32 buf[16];
const char __user *p = buffer;
size_t c = count;
size_t ret;
struct inode *inode = file->f_path.dentry->d_inode;
while (c > 0) {
bytes = min(c, sizeof(buf));
ret = write_pool(&blocking_pool, buffer, count);
if (ret)
return ret;
ret = write_pool(&nonblocking_pool, buffer, count);
if (ret)
return ret;
bytes -= copy_from_user(&buf, p, bytes);
if (!bytes) {
ret = -EFAULT;
break;
}
c -= bytes;
p += bytes;
add_entropy_words(&input_pool, buf, (bytes + 3) / 4);
}
if (p == buffer) {
return (ssize_t)ret;
} else {
struct inode *inode = file->f_path.dentry->d_inode;
inode->i_mtime = current_fs_time(inode->i_sb);
mark_inode_dirty(inode);
return (ssize_t)(p - buffer);
}
inode->i_mtime = current_fs_time(inode->i_sb);
mark_inode_dirty(inode);
return (ssize_t)count;
}
static int
@ -1089,8 +1096,8 @@ random_ioctl(struct inode * inode, struct file * file,
return -EINVAL;
if (get_user(size, p++))
return -EFAULT;
retval = random_write(file, (const char __user *) p,
size, &file->f_pos);
retval = write_pool(&input_pool, (const char __user *)p,
size);
if (retval < 0)
return retval;
credit_entropy_store(&input_pool, ent_count);