This is a note to let you know that I've just added the patch titled
PCI/IOV: Serialize sysfs sriov_numvfs reads vs writes
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pci-iov-serialize-sysfs-sriov_numvfs-reads-vs-writes.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d3b9e7c7ed11275853c42b7123774eb8646e0378
Author: Pierre Crégut <pierre.cregut@xxxxxxxxxx>
Date: Wed Sep 11 09:27:36 2019 +0200
PCI/IOV: Serialize sysfs sriov_numvfs reads vs writes
[ Upstream commit 35ff867b76576e32f34c698ccd11343f7d616204 ]
When sriov_numvfs is being updated, we call the driver->sriov_configure()
function, which may enable VFs and call probe functions, which may make new
devices visible. This all happens before before sriov_numvfs_store()
updates sriov->num_VFs, so previously, concurrent sysfs reads of
sriov_numvfs returned stale values.
Serialize the sysfs read vs the write so the read returns the correct
num_VFs value.
[bhelgaas: hold device_lock instead of checking mutex_is_locked()]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991
Link: https://lore.kernel.org/r/20190911072736.32091-1-pierre.cregut@xxxxxxxxxx
Signed-off-by: Pierre Crégut <pierre.cregut@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index deec9f9e0b616..9c116cbaa95d8 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -253,8 +253,14 @@ static ssize_t sriov_numvfs_show(struct device *dev,
char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
+ u16 num_vfs;
+
+ /* Serialize vs sriov_numvfs_store() so readers see valid num_VFs */
+ device_lock(&pdev->dev);
+ num_vfs = pdev->sriov->num_VFs;
+ device_unlock(&pdev->dev);
- return sprintf(buf, "%u\n", pdev->sriov->num_VFs);
+ return sprintf(buf, "%u\n", num_vfs);
}
/*
