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64 lines
2.0 KiB
Plaintext
64 lines
2.0 KiB
Plaintext
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From b381fbc509052d07ccf8641fd7560a25d46aaf1e Mon Sep 17 00:00:00 2001
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From: Ben Hutchings <ben@decadent.org.uk>
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Date: Sat, 13 Feb 2016 02:34:52 +0000
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Subject: pipe: Fix buffer offset after partially failed read
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Quoting the RHEL advisory:
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> It was found that the fix for CVE-2015-1805 incorrectly kept buffer
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> offset and buffer length in sync on a failed atomic read, potentially
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> resulting in a pipe buffer state corruption. A local, unprivileged user
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> could use this flaw to crash the system or leak kernel memory to user
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> space. (CVE-2016-0774, Moderate)
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The same flawed fix was applied to stable branches from 2.6.32.y to
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3.14.y inclusive, and I was able to reproduce the issue on 3.2.y.
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We need to give pipe_iov_copy_to_user() a separate offset variable
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and only update the buffer offset if it succeeds.
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References: https://rhn.redhat.com/errata/RHSA-2016-0103.html
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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Cc: Jeffrey Vander Stoep <jeffv@google.com>
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Signed-off-by: Zefan Li <lizefan@huawei.com>
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---
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fs/pipe.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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(limited to 'fs/pipe.c')
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diff --git a/fs/pipe.c b/fs/pipe.c
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index abfb935..6049235 100644
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--- a/fs/pipe.c
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+++ b/fs/pipe.c
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@@ -390,6 +390,7 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov,
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void *addr;
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size_t chars = buf->len, remaining;
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int error, atomic;
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+ int offset;
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if (chars > total_len)
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chars = total_len;
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@@ -403,9 +404,10 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov,
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atomic = !iov_fault_in_pages_write(iov, chars);
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remaining = chars;
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+ offset = buf->offset;
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redo:
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addr = ops->map(pipe, buf, atomic);
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- error = pipe_iov_copy_to_user(iov, addr, &buf->offset,
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+ error = pipe_iov_copy_to_user(iov, addr, &offset,
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&remaining, atomic);
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ops->unmap(pipe, buf, addr);
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if (unlikely(error)) {
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@@ -421,6 +423,7 @@ redo:
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break;
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}
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ret += chars;
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+ buf->offset += chars;
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buf->len -= chars;
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/* Was it a packet buffer? Clean up and exit */
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--
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cgit v1.1
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