This is a note to let you know that I've just added the patch titled
cxl/region: Fix cxl_region_rwsem lock held when returning to user space
to the 6.6-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:
cxl-region-fix-cxl_region_rwsem-lock-held-when-retur.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fea0766f75335ba1d6f35db24649c69aa398f92e
Author: Li Zhijian <lizhijian@xxxxxxxxxxx>
Date: Wed Oct 25 16:54:50 2023 +0800
cxl/region: Fix cxl_region_rwsem lock held when returning to user space
[ Upstream commit 3531b27f1f04a6bc9c95cf00d40efe618d57aa93 ]
Fix a missed "goto out" to unlock on error to cleanup this splat:
WARNING: lock held when returning to user space!
6.6.0-rc3-lizhijian+ #213 Not tainted
------------------------------------------------
cxl/673 is leaving the kernel with locks still held!
1 lock held by cxl/673:
#0: ffffffffa013b9d0 (cxl_region_rwsem){++++}-{3:3}, at: commit_store+0x7d/0x3e0 [cxl_core]
In terms of user visible impact of this bug for backports:
cxl_region_invalidate_memregion() on x86 invokes wbinvd which is a
problematic instruction for virtualized environments. So, on virtualized
x86, cxl_region_invalidate_memregion() returns an error. This failure
case got missed because CXL memory-expander device passthrough is not a
production use case, and emulation of CXL devices is typically limited
to kernel development builds with CONFIG_CXL_REGION_INVALIDATION_TEST=y,
that makes cxl_region_invalidate_memregion() succeed.
In other words, the expected exposure of this bug is limited to CXL
subsystem development environments using QEMU that neglected
CONFIG_CXL_REGION_INVALIDATION_TEST=y.
Fixes: d1257d098a5a ("cxl/region: Move cache invalidation before region teardown, and before setup")
Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Link: https://lore.kernel.org/r/20231025085450.2514906-1-lizhijian@xxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 644032cd680e4..d1f513800c10d 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -288,7 +288,7 @@ static ssize_t commit_store(struct device *dev, struct device_attribute *attr,
*/
rc = cxl_region_invalidate_memregion(cxlr);
if (rc)
- return rc;
+ goto out;
if (commit) {
rc = cxl_region_decode_commit(cxlr);
