Description
In the Linux kernel, the following vulnerability has been resolved: spi: spidev: fix lock inversion between spi_lock and buf_lock 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.
Product status
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before f8431b8672231d378b03176fe74c95adfd3522cf
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before e341e18215030af2136836b78508e0d798916df7
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before 41ccfac7d302968a4f32b5f7b012d066c5f5cdf8
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (git) before 40534d19ed2afb880ecf202dab26a8e7a5808d16
6.12.75 (semver)
6.18.16 (semver)
6.19.6 (semver)
7.0 (original_commit_for_fix)
References
git.kernel.org/...c/f8431b8672231d378b03176fe74c95adfd3522cf
git.kernel.org/...c/e341e18215030af2136836b78508e0d798916df7
git.kernel.org/...c/41ccfac7d302968a4f32b5f7b012d066c5f5cdf8
git.kernel.org/...c/40534d19ed2afb880ecf202dab26a8e7a5808d16