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| author | Ben Hutchings <ben@decadent.org.uk> | 2016-02-13 02:34:52 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-06-07 17:21:58 -0700 |
| commit | a952b0abde1c4502fd98fdba74859cb4ca6f4f78 (patch) | |
| tree | 48feea42ee3b7fdc8a3c737c77e314bc7e5ffa46 /fs | |
| parent | b459bc762398544e7d27cd543b5e72850f1e65c1 (diff) | |
| download | lwn-a952b0abde1c4502fd98fdba74859cb4ca6f4f78.tar.gz lwn-a952b0abde1c4502fd98fdba74859cb4ca6f4f78.zip | |
pipe: Fix buffer offset after partially failed read
commit feae3ca2e5e1a8f44aa6290255d3d9709985d0b2 upstream.
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>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -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 46f1ab264a4c..a03801186366 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -401,6 +401,7 @@ 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; @@ -414,9 +415,10 @@ 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 +434,7 @@ redo: break; } ret += chars; + buf->offset += chars; buf->len -= chars; /* Was it a packet buffer? Clean up and exit */ |