Commit c40374d5 authored by Simon Guinot's avatar Simon Guinot Committed by Luis Henriques

kernel/resource.c: fix muxed resource handling in __request_region()

commit 59ceeaaf 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: default avatarVincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: default avatarSimon Guinot <simon.guinot@sequanux.org>
Tested-by: default avatarVincent Donnefort <vdonnefort@gmail.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent c0c009a0
......@@ -957,9 +957,10 @@ 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);
......
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