linux-kernel - [PATCH] pci/msi: fix memory leak in free_msi

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Date:	Wed,  4 Jun 2014 15:49:50 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Neil Horman <nhorman@...driver.com>,
	"David S. Miller" <davem@...emloft.net>, linux-pci@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] pci/msi: fix memory leak in free_msi_irqs()

free_msi_irqs() is leaking memory, since
list_for_each_entry(entry, &dev->msi_list, list) {...}
is never executed, because dev->msi_list is made empty by
the loop just above this one.

Fix it by relying on zero termination of attribute array like
populate_msi_sysfs() does.

Fixes: 1c51b50c2995 ("PCI/MSI: Export MSI mode using attributes, not kobjects")
Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
---

This was found by kmemleak report:
unreferenced object 0xffff880808eda600 (size 64):
  comm "modprobe", pid 1526, jiffies 4294902299 (age 58422.716s)
  hex dump (first 32 bytes):
    20 c4 66 09 08 88 ff ff 24 01 00 00 00 00 00 00   .f.....$.......
    50 97 77 82 ff ff ff ff 00 00 00 00 00 00 00 00  P.w.............
  backtrace:
    [<ffffffff816e5fc8>] kmemleak_alloc+0x28/0x50
    [<ffffffff811b885e>] kmem_cache_alloc_trace+0xde/0x230
    [<ffffffff813aa286>] populate_msi_sysfs+0xc6/0x250
    [<ffffffff813aafdb>] pci_enable_msix+0x34b/0x430
    [<ffffffff813ab0ec>] pci_enable_msix_range+0x2c/0x70
    [<ffffffffa0034ade>] igb_init_interrupt_scheme+0x9e/0x420 [igb]
    [<ffffffffa003d668>] igb_probe+0x4a8/0x1250 [igb]
    [<ffffffff813930de>] local_pci_probe+0x4e/0xa0
    [<ffffffff813933e9>] pci_device_probe+0xd9/0x120
    [<ffffffff814697cd>] driver_probe_device+0x8d/0x250
    [<ffffffff81469a3b>] __driver_attach+0xab/0xb0
    [<ffffffff8146799d>] bus_for_each_dev+0x5d/0xa0
    [<ffffffff814691de>] driver_attach+0x1e/0x20
    [<ffffffff81468e57>] bus_add_driver+0x117/0x220
    [<ffffffff8146a104>] driver_register+0x64/0xf0
    [<ffffffff813923f4>] __pci_register_driver+0x64/0x70

IGB driver is calling pci_enable_msix_range() and immediately pci_disable_msix()
which leaks the memory.
Obviously the leak happens with any driver.

 drivers/pci/msi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 955ab7990c5b..fb02fc2fb034 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -414,7 +414,7 @@ static void free_msi_irqs(struct pci_dev *dev)
 	if (dev->msi_irq_groups) {
 		sysfs_remove_groups(&dev->dev.kobj, dev->msi_irq_groups);
 		msi_attrs = dev->msi_irq_groups[0]->attrs;
-		list_for_each_entry(entry, &dev->msi_list, list) {
+		while (msi_attrs[count]) {
 			dev_attr = container_of(msi_attrs[count],
 						struct device_attribute, attr);
 			kfree(dev_attr->attr.name);
-- 
1.7.9.5

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