kernel/linux.git/drivers/firmware/samsung, branch linux-7.1.y

firmware: samsung: acpm: Fix infinite loop on sequence number exhaustion

2026-05-29T12:11:23+00:00

Sashiko identified a possible infinite loop [1]. ACPM IPC sequence numbers are tracked via a 64-bit bitmap. Previously, acpm_prepare_xfer() used a do...while loop to search for a free sequence number. If all 63 available sequence numbers are leaked due to transient hardware timeouts or mailbox failures, the bitmap becomes full. The next call to acpm_prepare_xfer() would enter an infinite loop. Fix this by utilizing the kernel's optimized bitmap search functions (find_next_zero_bit / find_first_zero_bit). If the pool is completely exhausted, log the failure and return -EBUSY to allow the kernel to fail gracefully instead of hanging. Furthermore, drop the allocation loop entirely. Because acpm_prepare_xfer() is strictly called under the 'tx_lock' mutex, sequence number allocations are perfectly serialized. If find_next_zero_bit() locates a free bit, a single test_and_set_bit_lock() is mathematically guaranteed to succeed. To enforce this locking invariant, wrap the allocation in a WARN_ON_ONCE. If the atomic set fails, it indicates the driver's mutex serialization is fundamentally broken. The warning generates a stack trace for debugging, while returning -EIO immediately aborts the transfer to prevent silent payload corruption. Cc: stable@vger.kernel.org Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver") Closes: https://sashiko.dev/#/patchset/20260420-acpm-tmu-v3-0-3dc8e93f0b26%40linaro.org [1] Signed-off-by: Tudor Ambarus Link: https://patch.msgid.link/20260505-acpm-fixes-sashiko-reports-v5-7-43b5ee7f1674@linaro.org Signed-off-by: Krzysztof Kozlowski

firmware: samsung: acpm: Fix missing LKMM barriers in sequence allocator

2026-05-29T12:11:22+00:00

Sashiko identified memory ordering races in [1]. The ACPM driver uses a globally shared 'bitmap_seqnum' to track available sequence numbers. Even though threads now strictly free their own sequence numbers, the allocation and freeing of these bits across concurrent threads are effectively lockless operations and require explicit LKMM memory barriers. Previously, the driver used plain bitwise operators (test_bit, set_bit, clear_bit), which lack ordering guarantees. This creates two race conditions on weakly ordered architectures like ARM64: 1. Polling Release Violation: The polling thread copies its payload and calls clear_bit(). Without a release barrier, the CPU can reorder the memory operations, making the cleared bit globally visible before the payload reads have fully completed. 2. TX Acquire Violation: The TX thread loops on test_bit(), calls set_bit(), and then wipes the payload buffer via memset(). Without an acquire barrier, the CPU can speculatively execute the memset() before the bit is safely and formally claimed. If these reorderings overlap, a new TX thread can claim the sequence number and overwrite the buffer while the original polling thread is still actively reading from it. Fix this by upgrading the bitwise operators. Wrap the TX allocation in test_and_set_bit_lock() to establish formal LKMM Acquire semantics, and pair it with clear_bit_unlock() in the polling path to enforce Release semantics. Cc: stable@vger.kernel.org Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver") Closes: https://sashiko.dev/#/patchset/20260423-acpm-fixes-sashiko-reports-v1-0-2217b790925e%40linaro.org [1] Signed-off-by: Tudor Ambarus Link: https://patch.msgid.link/20260505-acpm-fixes-sashiko-reports-v5-6-43b5ee7f1674@linaro.org Signed-off-by: Krzysztof Kozlowski

firmware: samsung: acpm: Fix false timeouts and Use-After-Free in polling

2026-05-29T12:11:22+00:00

Sashiko identified severe races in the polling state machine [1]. In the ACPM driver's polling mode, threads waited for responses by monitoring the globally shared 'bitmap_seqnum'. This caused false timeouts because if a thread processed its response and freed the sequence number, a concurrent TX thread could immediately reallocate it before the polling thread woke up. Additionally, the driver suffered from a cross-thread Use-After-Free (UAF) preemption race. Previously, acpm_get_rx() cleared the sequence number of whichever RX message it drained from the hardware queue. This meant Thread A could globally free Thread B's sequence slot while Thread B was asleep. A new Thread C could then steal the slot, overwrite the buffer, and leave Thread B to wake up to corrupted state or a timeout. Fix this by rewriting the polling state machine: 1. Decouple polling from the global allocator by introducing a per-slot 'completed' flag, synchronized via smp_store_release() and smp_load_acquire(). 2. Strip acpm_get_saved_rx() out of acpm_get_rx() to make it a pure queue-draining function. Introduce a 'native_match' boolean argument which evaluates to true only if the thread natively processed its own sequence number during the call. This explicitly informs the polling loop whether it must retrieve its payload from the cross-thread cache. 3. Centralize the cache fallback and sequence number free (clear_bit) inside the polling loop. Crucially, the free operation now strictly targets the thread's own TX sequence number (xfer->txd[0]), rather than the drained RX sequence number. This enforces strict ownership: a thread only ever frees its own allocated sequence slot, and only at the exact moment it completes its poll, eliminating the UAF window. Furthermore, explicitly guard the 'native_match' assignment with an if (rx_seqnum == tx_seqnum) check, even for zero-length (no payload) responses. While an unguarded assignment wouldn't crash (because the cache fallback acpm_get_saved_rx() safely returns early on zero-length transfers) doing so would "lie" to the state machine. If a thread drained the queue and found another thread's zero-length message, setting native_match = true would falsely convince the polling loop that it natively handled its own response. Maintaining a rigorous state machine requires that native_match is only set when a thread explicitly processes its own sequence number. Cc: stable@vger.kernel.org Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver") Closes: https://sashiko.dev/#/patchset/20260429-acpm-fixes-sashiko-reports-v3-0-47cf74ab09ad%40linaro.org [1] Signed-off-by: Tudor Ambarus Link: https://patch.msgid.link/20260505-acpm-fixes-sashiko-reports-v5-5-43b5ee7f1674@linaro.org Signed-off-by: Krzysztof Kozlowski

firmware: samsung: acpm: Fix mailbox channel leak on probe error

2026-05-14T16:54:58+00:00

Sashiko identified the leak at [1]. The ACPM driver allocates hardware mailbox channels using `mbox_request_channel()` during `acpm_channels_init()`. However, the driver lacked a `.remove` callback and did not free these channels on subsequent error paths inside `acpm_probe()`. Additionally, if `acpm_achan_alloc_cmds()` failed during the channel initialization loop, the function returned immediately, bypassing the manual cleanup and permanently leaking any channels successfully requested in previous loop iterations. Fix this by modifying `acpm_free_mbox_chans()` to match the `devres` action signature and registering it via `devm_add_action_or_reset()`. Cc: stable@vger.kernel.org Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver") Closes: https://sashiko.dev/#/patchset/20260420-acpm-tmu-v3-0-3dc8e93f0b26%40linaro.org [1] Signed-off-by: Tudor Ambarus Link: https://patch.msgid.link/20260505-acpm-fixes-sashiko-reports-v5-2-43b5ee7f1674@linaro.org Signed-off-by: Krzysztof Kozlowski

firmware: samsung: acpm: Fix cross-thread RX length corruption

2026-05-14T16:54:34+00:00

Sashiko identified a cross-thread RX length corruption bug when reviewing the thermal addition to ACPM [1]. When multiple threads concurrently send IPC requests, the ACPM polling mechanism can encounter responses belonging to other threads. To drain the queue, the driver saves these concurrent responses into an internal cache (`rx_data->cmd`) to be retrieved later by the owning thread. Previously, the driver incorrectly used `xfer->rxcnt` (the expected receive length of the *current* polling thread) when copying data for *other* threads into this cache. If the threads expected responses of different lengths, this resulted in buffer underflows (leading to reads of uninitialized memory) or potential buffer overflows. Fix this by replacing the boolean `response` flag in `struct acpm_rx_data` with `rxcnt`, caching the exact expected receive length for each specific transaction during transfer preparation. Use this cached length when saving concurrent responses. Consequently, ensure that `xfer->rxcnt` is explicitly zeroed in driver helpers (e.g., `acpm_dvfs_set_xfer`) for fire-and-forget messages to prevent uninitialized stack garbage from being interpreted as a massive expected receive length. Cc: stable@vger.kernel.org Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver") Closes: https://sashiko.dev/#/patchset/20260420-acpm-tmu-v3-0-3dc8e93f0b26%40linaro.org [1] Reported-by: Titouan Ameline de Cadeville Closes: https://lore.kernel.org/r/20260426210255.73674-1-titouan.ameline@gmail.com/ Signed-off-by: Tudor Ambarus Link: https://patch.msgid.link/20260505-acpm-fixes-sashiko-reports-v5-1-43b5ee7f1674@linaro.org Signed-off-by: Krzysztof Kozlowski

firmware: exynos-acpm: Drop fake 'const' on handle pointer

2026-02-28T14:47:03+00:00

All the functions operating on the 'handle' pointer are claiming it is a pointer to const thus they should not modify the handle. In fact that's a false statement, because first thing these functions do is drop the cast to const with container_of: struct acpm_info *acpm = handle_to_acpm_info(handle); And with such cast the handle is easily writable with simple: acpm->handle.ops.pmic_ops.read_reg = NULL; The code is not correct logically, either, because functions like acpm_get_by_node() and acpm_handle_put() are meant to modify the handle reference counting, thus they must modify the handle. Modification here happens anyway, even if the reference counting is stored in the container which the handle is part of. The code does not have actual visible bug, but incorrect 'const' annotations could lead to incorrect compiler decisions. Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski Link: https://patch.msgid.link/20260224104203.42950-2-krzysztof.kozlowski@oss.qualcomm.com Signed-off-by: Krzysztof Kozlowski

firmware: exynos-acpm: Count acpm_xfer buffers with __counted_by_ptr

2026-02-24T11:06:30+00:00

Use __counted_by_ptr() attribute on the acpm_xfer buffers so UBSAN will validate runtime that we do not pass over the buffer size, thus making code safer. Usage of __counted_by_ptr() (or actually __counted_by()) requires that counter is initialized before counted array. Tested-by: Tudor Ambarus Reviewed-by: Tudor Ambarus Signed-off-by: Krzysztof Kozlowski Link: https://patch.msgid.link/20260219-firmare-acpm-counted-v2-3-e1f7389237d3@oss.qualcomm.com Signed-off-by: Krzysztof Kozlowski

firmware: exynos-acpm: Count number of commands in acpm_xfer

2026-02-24T11:06:29+00:00

Struct acpm_xfer holds two buffers with u32 commands - rxd and txd - and counts their size by rxlen and txlen. "len" suffix is here ambiguous, so could mean length of the buffer or length of commands, and these are not the same since each command is u32. Rename these to rxcnt and txcnt, and change their usage to count the number of commands in each buffer. This will have a benefit of allowing to use __counted_by_ptr later. Signed-off-by: Krzysztof Kozlowski Reviewed-by: Tudor Ambarus Link: https://patch.msgid.link/20260219-firmare-acpm-counted-v2-2-e1f7389237d3@oss.qualcomm.com Signed-off-by: Krzysztof Kozlowski

firmware: exynos-acpm: Use unsigned int for acpm_pmic_linux_errmap index

2026-02-24T11:06:29+00:00

acpm_pmic_to_linux_err() uses an unsigned integer obtained from messages as index of array to map them to error codes. Array index cannot be negative, so make that explicit. Reviewed-by: Tudor Ambarus Signed-off-by: Krzysztof Kozlowski Link: https://patch.msgid.link/20260219-firmare-acpm-counted-v2-1-e1f7389237d3@oss.qualcomm.com Signed-off-by: Krzysztof Kozlowski

firmware: exynos-acpm: register ACPM clocks pdev

2025-10-20T06:49:50+00:00

Register by hand a platform device for the ACPM clocks. The ACPM clocks are not modeled as a DT child of ACPM because: 1/ they don't have their own resources. 2/ they are not a block that can be reused. The clock identifying data is reduced (clock ID, clock name and mailbox channel ID) and may differ from a SoC to another. Signed-off-by: Tudor Ambarus Reviewed-by: Peter Griffin Tested-by: Peter Griffin # on gs101-oriole Link: https://patch.msgid.link/20251010-acpm-clk-v6-3-321ee8826fd4@linaro.org Signed-off-by: Krzysztof Kozlowski