Patch "cxl/region: Fix cxl_region_rwsem lock held when returning to user space" has been added to the 6.5-stable tree

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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 6.5-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-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit ae10eac6120c28afed892ca2094360ccbfd2efc3
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 89d24cd71606e..7392206eb8699 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);



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