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authorMarcin Slusarz <marcin.slusarz@gmail.com>2010-06-13 23:56:54 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-13 13:30:38 -0700
commit97537a758d5d29534ec0b280403c182fe5155ee5 (patch)
tree921cb11478ab453d661c6459a58bbf45e9d1326a /arch
parentafaac2588bac3673e5e1c6b73fc054c931535175 (diff)
downloadlinux-linaro-97537a758d5d29534ec0b280403c182fe5155ee5.tar.gz
x86, kmmio/mmiotrace: Fix double free of kmmio_fault_pages
commit 8b8f79b927b6b302bb65fb8c56e7a19be5fbdbef upstream. After every iounmap mmiotrace has to free kmmio_fault_pages, but it can't do it directly, so it defers freeing by RCU. It usually works, but when mmiotraced code calls ioremap-iounmap multiple times without sleeping between (so RCU won't kick in and start freeing) it can be given the same virtual address, so at every iounmap mmiotrace will schedule the same pages for release. Obviously it will explode on second free. Fix it by marking kmmio_fault_pages which are scheduled for release and not adding them second time. Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com> Tested-by: Marcin Kocielnicki <koriakin@0x04.net> Tested-by: Shinpei KATO <shinpei@il.is.s.u-tokyo.ac.jp> Acked-by: Pekka Paalanen <pq@iki.fi> Cc: Stuart Bennett <stuart@freedesktop.org> Cc: Marcin Kocielnicki <koriakin@0x04.net> Cc: nouveau@lists.freedesktop.org LKML-Reference: <20100613215654.GA3829@joi.lan> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/mm/kmmio.c16
-rw-r--r--arch/x86/mm/testmmiotrace.c22
2 files changed, 35 insertions, 3 deletions
diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index 5d0e67fff1a..e5d5e2ce9f7 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -45,6 +45,8 @@ struct kmmio_fault_page {
* Protected by kmmio_lock, when linked into kmmio_page_table.
*/
int count;
+
+ bool scheduled_for_release;
};
struct kmmio_delayed_release {
@@ -398,8 +400,11 @@ static void release_kmmio_fault_page(unsigned long page,
BUG_ON(f->count < 0);
if (!f->count) {
disarm_kmmio_fault_page(f);
- f->release_next = *release_list;
- *release_list = f;
+ if (!f->scheduled_for_release) {
+ f->release_next = *release_list;
+ *release_list = f;
+ f->scheduled_for_release = true;
+ }
}
}
@@ -471,8 +476,10 @@ static void remove_kmmio_fault_pages(struct rcu_head *head)
prevp = &f->release_next;
} else {
*prevp = f->release_next;
+ f->release_next = NULL;
+ f->scheduled_for_release = false;
}
- f = f->release_next;
+ f = *prevp;
}
spin_unlock_irqrestore(&kmmio_lock, flags);
@@ -510,6 +517,9 @@ void unregister_kmmio_probe(struct kmmio_probe *p)
kmmio_count--;
spin_unlock_irqrestore(&kmmio_lock, flags);
+ if (!release_list)
+ return;
+
drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC);
if (!drelease) {
pr_crit("leaking kmmio_fault_page objects.\n");
diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
index 8565d944f7c..38868adf07e 100644
--- a/arch/x86/mm/testmmiotrace.c
+++ b/arch/x86/mm/testmmiotrace.c
@@ -90,6 +90,27 @@ static void do_test(unsigned long size)
iounmap(p);
}
+/*
+ * Tests how mmiotrace behaves in face of multiple ioremap / iounmaps in
+ * a short time. We had a bug in deferred freeing procedure which tried
+ * to free this region multiple times (ioremap can reuse the same address
+ * for many mappings).
+ */
+static void do_test_bulk_ioremapping(void)
+{
+ void __iomem *p;
+ int i;
+
+ for (i = 0; i < 10; ++i) {
+ p = ioremap_nocache(mmio_address, PAGE_SIZE);
+ if (p)
+ iounmap(p);
+ }
+
+ /* Force freeing. If it will crash we will know why. */
+ synchronize_rcu();
+}
+
static int __init init(void)
{
unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
@@ -104,6 +125,7 @@ static int __init init(void)
"and writing 16 kB of rubbish in there.\n",
size >> 10, mmio_address);
do_test(size);
+ do_test_bulk_ioremapping();
pr_info("All done.\n");
return 0;
}