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backportable fix for copy_to_iter_mc() - the second part of

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iov_iter work will pretty much overwrite that one, but it's
 much harder to backport.
 
 Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Merge tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull copy_to_iter_mc fix from Al Viro:
 "Backportable fix for copy_to_iter_mc() - the second part of iov_iter
  work will pretty much overwrite this, but would be much harder to
  backport"

* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fix short copy handling in copy_mc_pipe_to_iter()
This commit is contained in:
Linus Torvalds 2022-08-03 13:59:15 -07:00
commit d9b58ab789
2 changed files with 20 additions and 4 deletions
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9
include/linux/pipe_fs_i.h
View File

@ -229,6 +229,15 @@ static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
return buf->ops->try_steal(pipe, buf);
}
static inline void pipe_discard_from(struct pipe_inode_info *pipe,
unsigned int old_head)
{
unsigned int mask = pipe->ring_size - 1;
while (pipe->head > old_head)
pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]);
}
/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
#define PIPE_SIZE PAGE_SIZE

15
lib/iov_iter.c
View File

@ -521,6 +521,7 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head;
unsigned int valid = pipe->head;
size_t n, off, xfer = 0;
if (!sanity(i))
@ -534,11 +535,17 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
chunk -= rem;
kunmap_local(p);
i->head = i_head;
i->iov_offset = off + chunk;
xfer += chunk;
if (rem)
if (chunk) {
i->head = i_head;
i->iov_offset = off + chunk;
xfer += chunk;
valid = i_head + 1;
}
if (rem) {
pipe->bufs[i_head & p_mask].len -= rem;
pipe_discard_from(pipe, valid);
break;
}
n -= chunk;
off = 0;
i_head++;