diff options
| author | Ben Hutchings <ben@decadent.org.uk> | 2016-02-13 05:34:52 +0300 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2016-02-27 17:28:49 +0300 |
| commit | feae3ca2e5e1a8f44aa6290255d3d9709985d0b2 (patch) | |
| tree | a2a2372876b0407218ff669911080eea32e7cf6f | |
| parent | 4249217f43bc2d1f0ba71895a566d28d8d097d52 (diff) | |
| download | linux-feae3ca2e5e1a8f44aa6290255d3d9709985d0b2.tar.xz | |
pipe: Fix buffer offset after partially failed read
Quoting the RHEL advisory:
> It was found that the fix for CVE-2015-1805 incorrectly kept buffer
> offset and buffer length in sync on a failed atomic read, potentially
> resulting in a pipe buffer state corruption. A local, unprivileged user
> could use this flaw to crash the system or leak kernel memory to user
> space. (CVE-2016-0774, Moderate)
The same flawed fix was applied to stable branches from 2.6.32.y to
3.14.y inclusive, and I was able to reproduce the issue on 3.2.y.
We need to give pipe_iov_copy_to_user() a separate offset variable
and only update the buffer offset if it succeeds.
References: https://rhn.redhat.com/errata/RHSA-2016-0103.html
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | fs/pipe.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 19078bd7beb8..bf3a99302d2a 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -395,6 +395,7 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov, void *addr; size_t chars = buf->len, remaining; int error, atomic; + int offset; if (chars > total_len) chars = total_len; @@ -408,9 +409,10 @@ 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)) { @@ -426,6 +428,7 @@ redo: break; } ret += chars; + buf->offset += chars; buf->len -= chars; /* Was it a packet buffer? Clean up and exit */ |