From: James Cowgill Date: Mon, 9 Jan 2017 16:52:28 +0000 (+0000) Subject: MIPS: OCTEON: Fix copy_from_user fault handling for large buffers X-Git-Tag: v3.2.89~50 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=29f5cc5dd4f1eda9658bbe3b00ab7dbbe082cfdd;p=pandora-kernel.git MIPS: OCTEON: Fix copy_from_user fault handling for large buffers commit 884b426917e4b3c85f33b382c792a94305dfdd62 upstream. If copy_from_user is called with a large buffer (>= 128 bytes) and the userspace buffer refers partially to unreadable memory, then it is possible for Octeon's copy_from_user to report the wrong number of bytes have been copied. In the case where the buffer size is an exact multiple of 128 and the fault occurs in the last 64 bytes, copy_from_user will report that all the bytes were copied successfully but leave some garbage in the destination buffer. The bug is in the main __copy_user_common loop in octeon-memcpy.S where in the middle of the loop, src and dst are incremented by 128 bytes. The l_exc_copy fault handler is used after this but that assumes that "src < THREAD_BUADDR($28)". This is not the case if src has already been incremented. Fix by adding an extra fault handler which rewinds the src and dst pointers 128 bytes before falling though to l_exc_copy. Thanks to the pwritev test from the strace test suite for originally highlighting this bug! Fixes: 5b3b16880f40 ("MIPS: Add Cavium OCTEON processor support ...") Signed-off-by: James Cowgill Acked-by: David Daney Reviewed-by: James Hogan Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/14978/ Signed-off-by: James Hogan Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed