3.2.79-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Simon Guinot <[email protected]> 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 <[email protected]> Signed-off-by: Simon Guinot <[email protected]> Tested-by: Vincent Donnefort <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/kernel/resource.c +++ b/kernel/resource.c @@ -886,9 +886,10 @@ struct resource * __request_region(struc 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);
