From 4bb62b96dc3d2ef4943d3b78b9db160f545a631f Mon Sep 17 00:00:00 2001 From: Jeff Vander Stoep Date: Wed, 23 Mar 2016 15:32:14 -0700 Subject: [PATCH] pipe: iovec: Fix OOB read in pipe_read() Previous upstream *stable* fix 14f81062 was incomplete. A local process can trigger a system crash with an OOB read on buf. This occurs when the state of buf gets out of sync. After an error in pipe_iov_copy_to_user() read_pipe may exit having updated buf->offset but not buf->len. Upon retrying pipe_read() while in pipe_iov_copy_to_user() *remaining will be larger than the space left after buf->offset e.g. *remaing = PAGE_SIZE, buf->len = PAGE_SIZE, buf->offset = 0x300. This is fixed by not updating the state of buf->offset until after the full copy is completed, similar to how pipe_write() is implemented. For stable kernels < 3.16. Bug: 27721803 Change-Id: Iefffbcc6cfd159dba69c31bcd98c6d5c1f21ff2e Signed-off-by: Jeff Vander Stoep --- fs/pipe.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 3e7ab278bb0c0..14b58f9f26f2e 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -400,7 +400,7 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov, const struct pipe_buf_operations *ops = buf->ops; void *addr; size_t chars = buf->len, remaining; - int error, atomic; + int error, atomic, offset; if (chars > total_len) chars = total_len; @@ -414,9 +414,10 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov, atomic = !iov_fault_in_pages_write(iov, chars); remaining = chars; + offset = buf->offset; redo: addr = ops->map(pipe, buf, atomic); - error = pipe_iov_copy_to_user(iov, addr, &buf->offset, + error = pipe_iov_copy_to_user(iov, addr, &offset, &remaining, atomic); ops->unmap(pipe, buf, addr); if (unlikely(error)) { @@ -432,6 +433,7 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov, break; } ret += chars; + buf->offset += chars; buf->len -= chars; /* Was it a packet buffer? Clean up and exit */