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Commit 9ff4a1a3 authored by Julius Werner's avatar Julius Werner Committed by Greg Kroah-Hartman
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drivers: char: mem: Fix wraparound check to allow mappings up to the end 



commit 32829da54d9368103a2f03269a5120aa9ee4d5da upstream.

A recent fix to /dev/mem prevents mappings from wrapping around the end
of physical address space. However, the check was written in a way that
also prevents a mapping reaching just up to the end of physical address
space, which may be a valid use case (especially on 32-bit systems).
This patch fixes it by checking the last mapped address (instead of the
first address behind that) for overflow.

Fixes: b299cde245 ("drivers: char: mem: Check for address space wraparound with mmap()")
Reported-by: default avatarNico Huber <nico.h@gmx.de>
Signed-off-by: default avatarJulius Werner <jwerner@chromium.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 106c77e8

drivers/char/mem.c

+1 −1
Original line number Diff line number Diff line
@@ -343,7 +343,7 @@ static int mmap_mem(struct file *file, struct vm_area_struct *vma) 
	phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;



	/* It's illegal to wrap around the end of the physical address space. */

	if (offset + (phys_addr_t)size < offset)

	if (offset + (phys_addr_t)size - 1 < offset)

		return -EINVAL;



	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))