Dan Williams ece3a3337c /dev/mem: Revoke mappings when a driver claims the region ... [ Upstream commit 3234ac664a ] Close the hole of holding a mapping over kernel driver takeover event of a given address range. Commit 90a545e981 ("restrict /dev/mem to idle io memory ranges") introduced CONFIG_IO_STRICT_DEVMEM with the goal of protecting the kernel against scenarios where a /dev/mem user tramples memory that a kernel driver owns. However, this protection only prevents *new* read(), write() and mmap() requests. Established mappings prior to the driver calling request_mem_region() are left alone. Especially with persistent memory, and the core kernel metadata that is stored there, there are plentiful scenarios for a /dev/mem user to violate the expectations of the driver and cause amplified damage. Teach request_mem_region() to find and shoot down active /dev/mem mappings that it believes it has successfully claimed for the exclusive use of the driver. Effectively a driver call to request_mem_region() becomes a hole-punch on the /dev/mem device. The typical usage of unmap_mapping_range() is part of truncate_pagecache() to punch a hole in a file, but in this case the implementation is only doing the "first half" of a hole punch. Namely it is just evacuating current established mappings of the "hole", and it relies on the fact that /dev/mem establishes mappings in terms of absolute physical address offsets. Once existing mmap users are invalidated they can attempt to re-establish the mapping, or attempt to continue issuing read(2) / write(2) to the invalidated extent, but they will then be subject to the CONFIG_IO_STRICT_DEVMEM checking that can block those subsequent accesses. Cc: Arnd Bergmann <arnd@arndb.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: 90a545e981 ("restrict /dev/mem to idle io memory ranges") Signed-off-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/159009507306.847224.8502634072429766747.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-06-24 17:50:35 +02:00
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asm-generic	mm: introduce MADV_PAGEOUT	2019-09-25 17:51:41 -07:00
drm	drm/amdgpu: return tcc_disabled_mask to userspace	2019-10-02 12:58:33 -05:00
linux	/dev/mem: Revoke mappings when a driver claims the region	2020-06-24 17:50:35 +02:00
misc	habanalabs: stop using the acronym KMD	2019-09-05 14:55:27 +03:00
mtd	mtd: abi: do not use C++ style comments in uapi header	2019-07-07 20:31:29 +02:00
rdma	rdma: Remove nes ABI header	2020-01-17 19:48:39 +01:00
scsi	scsi: use __u{8,16,32,64} instead of uint{8,16,32,64}_t in uapi headers	2019-08-12 22:19:27 -04:00
sound	Merge branch 'asoc-5.4' into asoc-next	2019-09-09 14:55:20 +01:00
video	…
xen	…
Kbuild	kbuild: re-implement Makefile.headersinst without recursion	2019-06-15 19:57:02 +09:00