163 lines
4.9 KiB
Diff
163 lines
4.9 KiB
Diff
From: Matthew Wilcox <willy@infradead.org>
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Date: Fri, 5 Apr 2019 14:02:10 -0700
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Subject: fs: prevent page refcount overflow in pipe_buf_get
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit?id=0311ff82b70fa12e80d188635bff24029ec06ae1
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2019-11487
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commit 15fab63e1e57be9fdb5eec1bbc5916e9825e9acb upstream.
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Change pipe_buf_get() to return a bool indicating whether it succeeded
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in raising the refcount of the page (if the thing in the pipe is a page).
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This removes another mechanism for overflowing the page refcount. All
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callers converted to handle a failure.
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Reported-by: Jann Horn <jannh@google.com>
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Signed-off-by: Matthew Wilcox <willy@infradead.org>
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Cc: stable@kernel.org
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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fs/fuse/dev.c | 12 ++++++------
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fs/pipe.c | 4 ++--
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fs/splice.c | 12 ++++++++++--
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include/linux/pipe_fs_i.h | 10 ++++++----
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kernel/trace/trace.c | 6 +++++-
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5 files changed, 29 insertions(+), 15 deletions(-)
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--- a/fs/fuse/dev.c
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+++ b/fs/fuse/dev.c
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@@ -1989,10 +1989,8 @@ static ssize_t fuse_dev_splice_write(str
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rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
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ret = -EINVAL;
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- if (rem < len) {
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- pipe_unlock(pipe);
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- goto out;
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- }
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+ if (rem < len)
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+ goto out_free;
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rem = len;
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while (rem) {
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@@ -2010,7 +2008,9 @@ static ssize_t fuse_dev_splice_write(str
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pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
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pipe->nrbufs--;
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} else {
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- pipe_buf_get(pipe, ibuf);
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+ if (!pipe_buf_get(pipe, ibuf))
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+ goto out_free;
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+
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*obuf = *ibuf;
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obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
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obuf->len = rem;
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@@ -2033,11 +2033,11 @@ static ssize_t fuse_dev_splice_write(str
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ret = fuse_dev_do_write(fud, &cs, len);
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pipe_lock(pipe);
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+out_free:
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for (idx = 0; idx < nbuf; idx++)
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pipe_buf_release(pipe, &bufs[idx]);
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pipe_unlock(pipe);
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-out:
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kvfree(bufs);
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return ret;
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}
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--- a/fs/pipe.c
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+++ b/fs/pipe.c
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@@ -189,9 +189,9 @@ EXPORT_SYMBOL(generic_pipe_buf_steal);
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* in the tee() system call, when we duplicate the buffers in one
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* pipe into another.
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*/
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-void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
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+bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
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{
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- get_page(buf->page);
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+ return try_get_page(buf->page);
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}
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EXPORT_SYMBOL(generic_pipe_buf_get);
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--- a/fs/splice.c
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+++ b/fs/splice.c
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@@ -1586,7 +1586,11 @@ retry:
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* Get a reference to this pipe buffer,
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* so we can copy the contents over.
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*/
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- pipe_buf_get(ipipe, ibuf);
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+ if (!pipe_buf_get(ipipe, ibuf)) {
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+ if (ret == 0)
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+ ret = -EFAULT;
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+ break;
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+ }
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*obuf = *ibuf;
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/*
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@@ -1660,7 +1664,11 @@ static int link_pipe(struct pipe_inode_i
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* Get a reference to this pipe buffer,
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* so we can copy the contents over.
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*/
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- pipe_buf_get(ipipe, ibuf);
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+ if (!pipe_buf_get(ipipe, ibuf)) {
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+ if (ret == 0)
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+ ret = -EFAULT;
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+ break;
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+ }
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obuf = opipe->bufs + nbuf;
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*obuf = *ibuf;
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--- a/include/linux/pipe_fs_i.h
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+++ b/include/linux/pipe_fs_i.h
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@@ -108,18 +108,20 @@ struct pipe_buf_operations {
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/*
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* Get a reference to the pipe buffer.
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*/
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- void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
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+ bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
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};
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/**
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* pipe_buf_get - get a reference to a pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to get a reference to
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+ *
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+ * Return: %true if the reference was successfully obtained.
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*/
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-static inline void pipe_buf_get(struct pipe_inode_info *pipe,
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+static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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- buf->ops->get(pipe, buf);
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+ return buf->ops->get(pipe, buf);
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}
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/**
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@@ -178,7 +180,7 @@ struct pipe_inode_info *alloc_pipe_info(
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void free_pipe_info(struct pipe_inode_info *);
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/* Generic pipe buffer ops functions */
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-void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
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+bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
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--- a/kernel/trace/trace.c
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+++ b/kernel/trace/trace.c
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@@ -6820,12 +6820,16 @@ static void buffer_pipe_buf_release(stru
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buf->private = 0;
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}
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-static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
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+static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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struct buffer_ref *ref = (struct buffer_ref *)buf->private;
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+ if (refcount_read(&ref->refcount) > INT_MAX/2)
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+ return false;
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+
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refcount_inc(&ref->refcount);
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+ return true;
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}
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/* Pipe buffer operations for a buffer. */
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