This is a note to let you know that I've just added the patch titled
fix short copy handling in copy_mc_pipe_to_iter()
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fix-short-copy-handling-in-copy_mc_pipe_to_iter.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c3497fd009ef2c59eea60d21c3ac22de3585ed7d Mon Sep 17 00:00:00 2001
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Sun, 12 Jun 2022 19:50:29 -0400
Subject: fix short copy handling in copy_mc_pipe_to_iter()
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
commit c3497fd009ef2c59eea60d21c3ac22de3585ed7d upstream.
Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
result in a short copy. In that case we need to trim the unused
buffers, as well as the length of partially filled one - it's not
enough to set ->head, ->iov_offset and ->count to reflect how
much had we copied. Not hard to fix, fortunately...
I'd put a helper (pipe_discard_from(pipe, head)) into pipe_fs_i.h,
rather than iov_iter.c - it has nothing to do with iov_iter and
having it will allow us to avoid an ugly kludge in fs/splice.c.
We could put it into lib/iov_iter.c for now and move it later,
but I don't see the point going that way...
Cc: stable@xxxxxxxxxx # 4.19+
Fixes: ca146f6f091e "lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe()"
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/pipe_fs_i.h | 9 +++++++++
lib/iov_iter.c | 15 +++++++++++----
2 files changed, 20 insertions(+), 4 deletions(-)
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -229,6 +229,15 @@ static inline bool pipe_buf_try_steal(st
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
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -689,6 +689,7 @@ static size_t copy_mc_pipe_to_iter(const
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))
@@ -702,11 +703,17 @@ static size_t copy_mc_pipe_to_iter(const
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++;
Patches currently in stable-queue which might be from viro@xxxxxxxxxxxxxxxxxx are
queue-5.19/vfs-check-the-truncate-maximum-size-in-inode_newsize_ok.patch
queue-5.19/fix-short-copy-handling-in-copy_mc_pipe_to_iter.patch
