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authorRobert Richter <rrichter@marvell.com>2019-11-21 21:36:57 +0000
committerBorislav Petkov <bp@suse.de>2019-11-22 09:53:08 +0100
commit16214bd9e43a31683a7073664b000029bba00354 (patch)
treedf95e4ea3a62b65ec80761ced66d24e31f955874 /drivers/edac
parent778f3a9673ac48bcf4c4ee640b2b29578cded8c1 (diff)
EDAC/ghes: Do not warn when incrementing refcount on 0
The following warning from the refcount framework is seen during ghes initialization: EDAC MC0: Giving out device to module ghes_edac.c controller ghes_edac: DEV ghes (INTERRUPT) ------------[ cut here ]------------ refcount_t: increment on 0; use-after-free. WARNING: CPU: 36 PID: 1 at lib/refcount.c:156 refcount_inc_checked [...] Call trace: refcount_inc_checked ghes_edac_register ghes_probe ... It warns if the refcount is incremented from zero. This warning is reasonable as a kernel object is typically created with a refcount of one and freed once the refcount is zero. Afterwards the object would be "used-after-free". For GHES, the refcount is initialized with zero, and that is why this message is seen when initializing the first instance. However, whenever the refcount is zero, the device will be allocated and registered. Since the ghes_reg_mutex protects the refcount and serializes allocation and freeing of ghes devices, a use-after-free cannot happen here. Instead of using refcount_inc() for the first instance, use refcount_set(). This can be used here because the refcount is zero at this point and can not change due to its protection by the mutex. Fixes: 23f61b9fc5cc ("EDAC/ghes: Fix locking and memory barrier issues") Reported-by: John Garry <john.garry@huawei.com> Signed-off-by: Robert Richter <rrichter@marvell.com> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: John Garry <john.garry@huawei.com> Cc: <huangming23@huawei.com> Cc: James Morse <james.morse@arm.com> Cc: <linuxarm@huawei.com> Cc: linux-edac <linux-edac@vger.kernel.org> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: <tanxiaofei@huawei.com> Cc: Tony Luck <tony.luck@intel.com> Cc: <wanghuiqiang@huawei.com> Link: https://lkml.kernel.org/r/20191121213628.21244-1-rrichter@marvell.com
Diffstat (limited to 'drivers/edac')
-rw-r--r--drivers/edac/ghes_edac.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c
index 47f4e7f90ef0..b99080d8a10c 100644
--- a/drivers/edac/ghes_edac.c
+++ b/drivers/edac/ghes_edac.c
@@ -556,8 +556,8 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev)
ghes_pvt = pvt;
spin_unlock_irqrestore(&ghes_lock, flags);
- /* only increment on success */
- refcount_inc(&ghes_refcount);
+ /* only set on success */
+ refcount_set(&ghes_refcount, 1);
unlock:
mutex_unlock(&ghes_reg_mutex);