From: Fabian Godehardt <fg@emlix.com> stable inclusion from stable-v6.12.75 commit f8431b8672231d378b03176fe74c95adfd3522cf category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14877 CVE: CVE-2026-43319 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 40534d19ed2afb880ecf202dab26a8e7a5808d16 ] The spidev driver previously used two mutexes, spi_lock and buf_lock, but acquired them in different orders depending on the code path: write()/read(): buf_lock -> spi_lock ioctl(): spi_lock -> buf_lock This AB-BA locking pattern triggers lockdep warnings and can cause real deadlocks: WARNING: possible circular locking dependency detected spidev_ioctl() -> mutex_lock(&spidev->buf_lock) spidev_sync_write() -> mutex_lock(&spidev->spi_lock) *** DEADLOCK *** The issue is reproducible with a simple userspace program that performs write() and SPI_IOC_WR_MAX_SPEED_HZ ioctl() calls from separate threads on the same spidev file descriptor. Fix this by simplifying the locking model and removing the lock inversion entirely. spidev_sync() no longer performs any locking, and all callers serialize access using spi_lock. buf_lock is removed since its functionality is fully covered by spi_lock, eliminating the possibility of lock ordering issues. This removes the lock inversion and prevents deadlocks without changing userspace ABI or behaviour. Signed-off-by: Fabian Godehardt <fg@emlix.com> Link: https://patch.msgid.link/20260211072616.489522-1-fg@emlix.com Signed-off-by: Mark Brown <broonie@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: drivers/spi/spidev.c [Context Conflicts] Signed-off-by: Lin Ruifeng <linruifeng4@huawei.com> --- drivers/spi/spidev.c | 64 +++++++++++++++----------------------------- 1 file changed, 22 insertions(+), 42 deletions(-) diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index 1c072a6e947e..f7b658ec0e7f 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -72,7 +72,6 @@ struct spidev_data { struct list_head device_entry; /* TX/RX buffers are NULL unless this device is open (users > 0) */ - struct mutex buf_lock; unsigned users; u8 *tx_buffer; u8 *rx_buffer; @@ -100,25 +99,6 @@ spidev_sync_unlocked(struct spi_device *spi, struct spi_message *message) return status; } -static ssize_t -spidev_sync(struct spidev_data *spidev, struct spi_message *message) -{ - ssize_t status; - struct spi_device *spi; - - mutex_lock(&spidev->spi_lock); - spi = spidev->spi; - - if (spi == NULL) - status = -ESHUTDOWN; - else - status = spidev_sync_unlocked(spi, message); - - mutex_unlock(&spidev->spi_lock); - - return status; -} - static inline ssize_t spidev_sync_write(struct spidev_data *spidev, size_t len) { @@ -131,7 +111,8 @@ spidev_sync_write(struct spidev_data *spidev, size_t len) spi_message_init(&m); spi_message_add_tail(&t, &m); - return spidev_sync(spidev, &m); + + return spidev_sync_unlocked(spidev->spi, &m); } static inline ssize_t @@ -146,7 +127,8 @@ spidev_sync_read(struct spidev_data *spidev, size_t len) spi_message_init(&m); spi_message_add_tail(&t, &m); - return spidev_sync(spidev, &m); + + return spidev_sync_unlocked(spidev->spi, &m); } /*-------------------------------------------------------------------------*/ @@ -156,7 +138,7 @@ static ssize_t spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { struct spidev_data *spidev; - ssize_t status; + ssize_t status = -ESHUTDOWN; /* chipselect only toggles at start or end of operation */ if (count > bufsiz) @@ -164,7 +146,11 @@ spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) spidev = filp->private_data; - mutex_lock(&spidev->buf_lock); + mutex_lock(&spidev->spi_lock); + + if (spidev->spi == NULL) + goto err_spi_removed; + status = spidev_sync_read(spidev, count); if (status > 0) { unsigned long missing; @@ -175,7 +161,9 @@ spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) else status = status - missing; } - mutex_unlock(&spidev->buf_lock); + +err_spi_removed: + mutex_unlock(&spidev->spi_lock); return status; } @@ -186,7 +174,7 @@ spidev_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos) { struct spidev_data *spidev; - ssize_t status; + ssize_t status = -ESHUTDOWN; unsigned long missing; /* chipselect only toggles at start or end of operation */ @@ -195,13 +183,19 @@ spidev_write(struct file *filp, const char __user *buf, spidev = filp->private_data; - mutex_lock(&spidev->buf_lock); + mutex_lock(&spidev->spi_lock); + + if (spidev->spi == NULL) + goto err_spi_removed; + missing = copy_from_user(spidev->tx_buffer, buf, count); if (missing == 0) status = spidev_sync_write(spidev, count); else status = -EFAULT; - mutex_unlock(&spidev->buf_lock); + +err_spi_removed: + mutex_unlock(&spidev->spi_lock); return status; } @@ -375,14 +369,6 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) return -ESHUTDOWN; } - /* use the buffer lock here for triple duty: - * - prevent I/O (from us) so calling spi_setup() is safe; - * - prevent concurrent SPI_IOC_WR_* from morphing - * data fields while SPI_IOC_RD_* reads them; - * - SPI_IOC_MESSAGE needs the buffer locked "normally". - */ - mutex_lock(&spidev->buf_lock); - switch (cmd) { /* read requests */ case SPI_IOC_RD_MODE: @@ -508,7 +494,6 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) break; } - mutex_unlock(&spidev->buf_lock); spi_dev_put(spi); mutex_unlock(&spidev->spi_lock); return retval; @@ -539,9 +524,6 @@ spidev_compat_ioc_message(struct file *filp, unsigned int cmd, return -ESHUTDOWN; } - /* SPI_IOC_MESSAGE needs the buffer locked "normally" */ - mutex_lock(&spidev->buf_lock); - /* Check message and copy into scratch area */ ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc); if (IS_ERR(ioc)) { @@ -562,7 +544,6 @@ spidev_compat_ioc_message(struct file *filp, unsigned int cmd, kfree(ioc); done: - mutex_unlock(&spidev->buf_lock); spi_dev_put(spi); mutex_unlock(&spidev->spi_lock); return retval; @@ -772,7 +753,6 @@ static int spidev_probe(struct spi_device *spi) /* Initialize the driver data */ spidev->spi = spi; mutex_init(&spidev->spi_lock); - mutex_init(&spidev->buf_lock); INIT_LIST_HEAD(&spidev->device_entry); -- 2.43.0