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This fix is applicable for LTS kernel, 6.1.y. In latest kernels, this race issue is fixed by the patch series [1] and [2]. The right thing to do here would have been propagating these changes from latest kernel to the stable branch, 6.1.y. However, these changes seems too intrusive to be picked for stable branches. Hence, the fix proposed can be taken as an alternative instead of backporting the patch series. [1] https://lore.kernel.org/all/0-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.com/ [2] https://lore.kernel.org/all/0-v5-1b99ae392328+44574-iommu_err_unwind_jgg@nvidia.com/ Issue: A race condition is observed when arm_smmu_device_probe and modprobe of client devices happens in parallel. This results in the allocation of a new default domain for the iommu group even though it was previously allocated and the respective iova domain(iovad) was initialized. However, for this newly allocated default domain, iovad will not be initialized. As a result, for devices requesting dma allocations, this uninitialized iovad will be used, thereby causing NULL pointer dereference issue. Flow: - During arm_smmu_device_probe, bus_iommu_probe() will be called as part of iommu_device_register(). This results in the device probe, __iommu_probe_device(). - When the modprobe of the client device happens in parallel, it sets up the DMA configuration for the device using of_dma_configure_id(), which inturn calls iommu_probe_device(). Later, default domain is allocated and attached using iommu_alloc_default_domain() and __iommu_attach_device() respectively. It then ends up initializing a mapping domain(IOVA domain) and rcaches for the device via arch_setup_dma_ops()->iommu_setup_dma_ops(). - Now, in the bus_iommu_probe() path, it again tries to allocate a default domain via probe_alloc_default_domain(). This results in allocating a new default domain(along with IOVA domain) via __iommu_domain_alloc(). However, this newly allocated IOVA domain will not be initialized. - Now, when the same client device tries dma allocations via iommu_dma_alloc(), it ends up accessing the rcaches of the newly allocated IOVA domain, which is not initialized. This results into NULL pointer dereferencing. Fix this issue by adding a check in probe_alloc_default_domain() to see if the iommu_group already has a default domain allocated and initialized. Adding a check in iommu_group_alloc_default_domain would not allow changing the default domain for an iommu group, via, iommu_change_dev_def_domain. As per the suggestions from upstream review for patch [3], the check for default domain was moved and duplicated into the callers, thereby restricting it only to the probe paths. [3] https://lore.kernel.org/all/e605b38a2d40b1e7589e10110c6d3ece35f6af4e.1705571894.git.quic_nprakash@quicinc.com/ Bug: 317188933 Link: https://lore.kernel.org/all/cbf1295589bd90083ad6f75a7fbced01f327c047.1708680521.git.quic_nprakash@quicinc.com/ Change-Id: I060d5b796911b1a597495d003e83cff0fd8b7625 Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com> Co-developed-by: Nikhil V <quic_nprakash@quicinc.com> Signed-off-by: Nikhil V <quic_nprakash@quicinc.com>
How do I submit patches to Android Common Kernels
-
BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.
- Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux,
additions of
EXPORT_SYMBOL_GPL()require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export. - When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.
- Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux,
additions of
-
LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.
Common Kernel patch requirements
- All patches must conform to the Linux kernel coding standards and pass
scripts/checkpatch.pl - Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
- If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch:
UPSTREAM:,BACKPORT:,FROMGIT:,FROMLIST:, orANDROID:. - All patches must have a
Change-Id:tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html) - If an Android bug has been assigned, there must be a
Bug:tag. - All patches must have a
Signed-off-by:tag by the author and the submitter
Additional requirements are listed below based on patch type
Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:
- If the patch is a cherry-pick from Linux mainline with no changes at all
- tag the patch subject with
UPSTREAM:. - add upstream commit information with a
(cherry picked from commit ...)line - Example:
- if the upstream commit message is
- tag the patch subject with
important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
UPSTREAM: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
(cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch requires any changes from the upstream version, tag the patch with
BACKPORT:instead ofUPSTREAM:.- use the same tags as
UPSTREAM: - add comments about the changes under the
(cherry picked from commit ...)line - Example:
- use the same tags as
BACKPORT: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
(cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
[joe: Resolved minor conflict in drivers/foo/bar.c ]
Signed-off-by: Joe Smith <joe.smith@foo.org>
Requirements for other backports: FROMGIT:, FROMLIST:,
- If the patch has been merged into an upstream maintainer tree, but has not yet
been merged into Linux mainline
- tag the patch subject with
FROMGIT: - add info on where the patch came from as
(cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't uselinux-nextfor example). - if changes were required, use
BACKPORT: FROMGIT: - Example:
- if the commit message in the maintainer tree is
- tag the patch subject with
important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
FROMGIT: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
(cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch has been submitted to LKML, but not accepted into any maintainer tree
- tag the patch subject with
FROMLIST: - add a
Link:tag with a link to the submittal on lore.kernel.org - add a
Bug:tag with the Android bug (required for patches not accepted into a maintainer tree) - if changes were required, use
BACKPORT: FROMLIST: - Example:
- tag the patch subject with
FROMLIST: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
Requirements for Android-specific patches: ANDROID:
- If the patch is fixing a bug to Android-specific code
- tag the patch subject with
ANDROID: - add a
Fixes:tag that cites the patch with the bug - Example:
- tag the patch subject with
ANDROID: fix android-specific bug in foobar.c
This is the detailed description of the important fix
Fixes: 1234abcd2468 ("foobar: add cool feature")
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch is a new feature
- tag the patch subject with
ANDROID: - add a
Bug:tag with the Android bug (required for android-specific features)
- tag the patch subject with