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[MIPS] Add len and addr validation for MAP_FIXED mappings.
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Mmap with MAP_FIXED was not validating the addr and len parameters.  This
leads to the failure of GCC's gcc.c-torture/execute/loop-2[fg].c testcases
when using the o32 ABI on a 64 bit kernel.

These testcases try to mmap 65536 bytes at 0x7fff8000 and then access all
the memory.  In 2.6.18 and 2.6.23.1 (and likely other versions as well)
the kernel maps the requested memory, but since half of it is above
0x80000000 a SIGBUS is generated when it is accessed.

This patch moves the len validation above the MAP_FIXED processing so that
it is always validated.  It also adds validation to the addr parameter for
MAP_FIXED mappings.

Signed-off-by: David Daney  <ddaney@avtrex.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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David Daney authored and Ralf Baechle committed Oct 29, 2007
1 parent c4e8308 commit 098362e
Showing 1 changed file with 7 additions and 2 deletions.
9 changes: 7 additions & 2 deletions arch/mips/kernel/syscall.c
Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,14 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,

task_size = STACK_TOP;

if (len > task_size)
return -ENOMEM;

if (flags & MAP_FIXED) {
/* Even MAP_FIXED mappings must reside within task_size. */
if (task_size - len < addr)
return -EINVAL;

/*
* We do not accept a shared mapping if it would violate
* cache aliasing constraints.
Expand All @@ -83,8 +90,6 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
return addr;
}

if (len > task_size)
return -ENOMEM;
do_color_align = 0;
if (filp || (flags & MAP_SHARED))
do_color_align = 1;
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