| From | Kamal Mostafa <> | Subject | [PATCH 3.13.y-ckt 105/138] kernel/resource.c: fix muxed resource handling in __request_region() | Date | Wed, 9 Mar 2016 15:13:52 -0800 |
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3.13.11-ckt36 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Simon Guinot <simon.guinot@sequanux.org>
commit 59ceeaaf355fa0fb16558ef7c24413c804932ada upstream.
In __request_region, if a conflict with a BUSY and MUXED resource is detected, then the caller goes to sleep and waits for the resource to be released. A pointer on the conflicting resource is kept. At wake-up this pointer is used as a parent to retry to request the region.
A first problem is that this pointer might well be invalid (if for example the conflicting resource have already been freed). Another problem is that the next call to __request_region() fails to detect a remaining conflict. The previously conflicting resource is passed as a parameter and __request_region() will look for a conflict among the children of this resource and not at the resource itself. It is likely to succeed anyway, even if there is still a conflict.
Instead, the parent of the conflicting resource should be passed to __request_region().
As a fix, this patch doesn't update the parent resource pointer in the case we have to wait for a muxed region right after.
Reported-and-tested-by: Vincent Pelletier <plr.vincent@gmail.com> Signed-off-by: Simon Guinot <simon.guinot@sequanux.org> Tested-by: Vincent Donnefort <vdonnefort@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/resource.c b/kernel/resource.c index 3f285dc..449282e 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -961,9 +961,10 @@ struct resource * __request_region(struct resource *parent, if (!conflict) break; if (conflict != parent) { - parent = conflict; - if (!(conflict->flags & IORESOURCE_BUSY)) + if (!(conflict->flags & IORESOURCE_BUSY)) { + parent = conflict; continue; + } } if (conflict->flags & flags & IORESOURCE_MUXED) { add_wait_queue(&muxed_resource_wait, &wait); -- 2.7.0
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