On 2/3/2016 1:52 PM, Ian Campbell wrote:
On Wed, 2016-02-03 at 13:37 +0200, Corneliu ZUZU wrote:
I just now applied a previous v2 which was already in my queue. Was this
just an accidental resend of v2 or is there some important change and this
is really a v3?
When __p2m_get_mem_access gets called, the p2m lock is already taken
by either get_page_from_gva or p2m_get_mem_access.
Possible code paths:
1) -> get_page_from_gva
-> p2m_mem_access_check_and_get_page
-> __p2m_get_mem_access
2) -> p2m_get_mem_access
-> __p2m_get_mem_access
In both cases if __p2m_get_mem_access subsequently gets to
call p2m_lookup (happens if !radix_tree_lookup(...)), a hypervisor
hang will occur, since p2m_lookup also spin-locks on the p2m lock.
This bug-fix simply replaces the p2m_lookup call from
__p2m_get_mem_access
with a call to __p2m_lookup and also adds an ASSERT to ensure that the
p2m lock
is already taken upon __p2m_get_mem_access entry.
Signed-off-by: Corneliu ZUZU <cz...@bitdefender.com>
---
Changed since v1:
* added p2m-lock ASSERT
---
xen/arch/arm/p2m.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 2190908..e8e6db4 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -468,6 +468,8 @@ static int __p2m_get_mem_access(struct domain *d,
gfn_t gfn,
#undef ACCESS
};
+ ASSERT(spin_is_locked(&p2m->lock));
+
/* If no setting was ever set, just return rwx. */
if ( !p2m->mem_access_enabled )
{
@@ -490,7 +492,7 @@ static int __p2m_get_mem_access(struct domain *d,
gfn_t gfn,
* No setting was found in the Radix tree. Check if the
* entry exists in the page-tables.
*/
- paddr_t maddr = p2m_lookup(d, gfn_x(gfn) << PAGE_SHIFT, NULL);
+ paddr_t maddr = __p2m_lookup(d, gfn_x(gfn) << PAGE_SHIFT, NULL);
if ( INVALID_PADDR == maddr )
return -ESRCH;
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No, sorry, this is just a duplicate of the 1st v2, I thought the first
one was not sent properly (after waiting a few days and noticing
I was no longer finding it on the web).
Ignore this one. And thanks.
Corneliu.
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