linux/arch/sparc
Kirill A. Shutemov 4ecf886045 sparc32: fix broken set_pte()
32-bit sparc uses swap instruction to implement set_pte().  It called
using GCC inline assembler.  But it misses the "memory" clobber to
indicate that pte value will be updated in memory.

As result GCC doesn't know that it cannot postpone pte pointer dereference
which occurs before set_pte() to post-set_pte() time.

It leads to real-world bugs -- [1]. In this situation we have code:

	ptent = ptep_modify_prot_start(mm, addr, pte);
	ptent = pte_modify(ptent, newprot);
	...
	ptep_modify_prot_commit(mm, addr, pte, ptent);

ptep_modify_prot_start() in sparc case is just 'pte' dereference plus
pte_clear().  pte_clear() calls broken set_pte().  GCC thinks it's valid
to dereference 'pte' again on pte_modify() and gets cleared pte.
ptep_modify_prot_commit() puts 'pteent' with pfn==0 back to page table,
which eventually leads to the crash.

[1] http://lkml.kernel.org/r/54C06B19.8060305@roeck-us.net

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: Paul Moore <pmoore@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-11 17:06:01 -08:00
..
boot sparc: Add "install" target 2014-08-04 20:45:59 -07:00
configs sparc: Set CONFIG_NET=y in defconfigs 2014-09-24 13:38:30 -04:00
crypto crypto: sparc - replace memset by memzero_explicit 2014-12-02 22:55:48 +08:00
include sparc32: fix broken set_pte() 2015-02-11 17:06:01 -08:00
kernel sparc/PCI: Clip bridge windows to fit in upstream windows 2015-01-16 10:04:43 -06:00
lib sparc32: Implement xchg and atomic_xchg using ATOMIC_HASH locks 2014-11-07 12:51:44 -08:00
math-emu arch/sparc/math-emu/math_32.c: drop stray break operator 2014-08-04 20:29:06 -07:00
mm mm/hugetlb: reduce arch dependent code around follow_huge_* 2015-02-11 17:06:01 -08:00
net module: remove mod arg from module_free, rename module_memfree(). 2015-01-20 11:38:33 +10:30
oprofile
power Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2014-10-11 20:36:34 -04:00
prom sparc64: Fix register corruption in top-most kernel stack frame during boot. 2014-10-24 09:52:49 -07:00
Kbuild sparc64: Add SHA1 driver making use of the 'sha1' instruction. 2012-08-20 15:08:49 -07:00
Kconfig sparc64: sparse irq 2014-10-05 16:53:40 -07:00
Kconfig.debug
Makefile sparc: Add "install" target 2014-08-04 20:45:59 -07:00