This is a note to let you know that I've just added the patch titled
cxl/memdev: Hold region_rwsem during inject and clear poison ops
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-memdev-hold-region_rwsem-during-inject-and-clear-poison-ops.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.
>From 0e33ac9c3ffe5e4f55c68345f44cea7fec2fe750 Mon Sep 17 00:00:00 2001
From: Alison Schofield <alison.schofield@xxxxxxxxx>
Date: Sun, 26 Nov 2023 16:09:30 -0800
Subject: cxl/memdev: Hold region_rwsem during inject and clear poison ops
From: Alison Schofield <alison.schofield@xxxxxxxxx>
commit 0e33ac9c3ffe5e4f55c68345f44cea7fec2fe750 upstream.
Poison inject and clear are supported via debugfs where a privileged
user can inject and clear poison to a device physical address.
Commit 458ba8189cb4 ("cxl: Add cxl_decoders_committed() helper")
added a lockdep assert that highlighted a gap in poison inject and
clear functions where holding the dpa_rwsem does not assure that a
a DPA is not added to a region.
The impact for inject and clear is that if the DPA address being
injected or cleared has been attached to a region, but not yet
committed, the dev_dbg() message intended to alert the debug user
that they are acting on a mapped address is not emitted. Also, the
cxl_poison trace event that serves as a log of the inject and clear
activity will not include region info.
Close this gap by snapshotting an unchangeable region state during
poison inject and clear operations. That means holding both the
region_rwsem and the dpa_rwsem during the inject and clear ops.
Fixes: d2fbc4865802 ("cxl/memdev: Add support for the Inject Poison mailbox command")
Fixes: 9690b07748d1 ("cxl/memdev: Add support for the Clear Poison mailbox command")
Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Link: https://lore.kernel.org/r/08721dc1df0a51e4e38fecd02425c3475912dfd5.1701041440.git.alison.schofield@xxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/cxl/core/memdev.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -331,10 +331,16 @@ int cxl_inject_poison(struct cxl_memdev
if (!IS_ENABLED(CONFIG_DEBUG_FS))
return 0;
- rc = down_read_interruptible(&cxl_dpa_rwsem);
+ rc = down_read_interruptible(&cxl_region_rwsem);
if (rc)
return rc;
+ rc = down_read_interruptible(&cxl_dpa_rwsem);
+ if (rc) {
+ up_read(&cxl_region_rwsem);
+ return rc;
+ }
+
rc = cxl_validate_poison_dpa(cxlmd, dpa);
if (rc)
goto out;
@@ -362,6 +368,7 @@ int cxl_inject_poison(struct cxl_memdev
trace_cxl_poison(cxlmd, cxlr, &record, 0, 0, CXL_POISON_TRACE_INJECT);
out:
up_read(&cxl_dpa_rwsem);
+ up_read(&cxl_region_rwsem);
return rc;
}
@@ -379,10 +386,16 @@ int cxl_clear_poison(struct cxl_memdev *
if (!IS_ENABLED(CONFIG_DEBUG_FS))
return 0;
- rc = down_read_interruptible(&cxl_dpa_rwsem);
+ rc = down_read_interruptible(&cxl_region_rwsem);
if (rc)
return rc;
+ rc = down_read_interruptible(&cxl_dpa_rwsem);
+ if (rc) {
+ up_read(&cxl_region_rwsem);
+ return rc;
+ }
+
rc = cxl_validate_poison_dpa(cxlmd, dpa);
if (rc)
goto out;
@@ -419,6 +432,7 @@ int cxl_clear_poison(struct cxl_memdev *
trace_cxl_poison(cxlmd, cxlr, &record, 0, 0, CXL_POISON_TRACE_CLEAR);
out:
up_read(&cxl_dpa_rwsem);
+ up_read(&cxl_region_rwsem);
return rc;
}
Patches currently in stable-queue which might be from alison.schofield@xxxxxxxxx are
queue-6.6/cxl-add-cxl_decoders_committed-helper.patch
queue-6.6/cxl-core-always-hold-region_rwsem-while-reading-pois.patch
queue-6.6/kernel-resource-increment-by-align-value-in-get_free.patch
queue-6.6/cxl-add-cxl_num_decoders_committed-usage-to-cxl_test.patch
queue-6.6/cxl-memdev-hold-region_rwsem-during-inject-and-clear-poison-ops.patch
