Linux Linux Kernel vulnerabilities

In the Linux kernel, the following vulnerability has been resolved: fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() may_decode_fh() accesses mount::mnt_ns without holding any locks; that means the mount can concurrently be unmounted, and the mnt_namespace can concurrently be freed after an RCU grace period. This race can happens as follows, assuming that the mount point was created by open_tree(..., OPEN_TREE_CLONE): thread 1 thread 2 RCU __do_sys_open_by_handle_at do_handle_open handle_to_path may_decode_fh is_mounted [mount::mnt_ns access] [mount::mnt_ns access] __do_sys_close fput_close_sync __fput dissolve_on_fput umount_tree class_namespace_excl_destructor namespace_unlock free_mnt_ns mnt_ns_tree_remove call_rcu(mnt_ns_release_rcu) mnt_ns_release_rcu mnt_ns_release kfree [mnt_namespace::user_ns access] **UAF** Fix it by taking rcu_read_lock() around the mount::mnt_ns access, like in __prepend_path(). Additionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE() for writers that can race with lockless readers. This bug is unreachable unless one of the following is set: - CONFIG_PREEMPTION - CONFIG_RCU_STRICT_GRACE_PERIOD because it requires an RCU grace period to happen during a syscall without an explicit preemption. This doesn't seem to have interesting security impact; worst-case, it could leak the result of an integer comparison to userspace (from the level check in cap_capable()), cause an endless loop, or crash the kernel by dereferencing an invalid address.

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Fix out-of-bounds read in dp_get_eq_aux_rd_interval() [Why & How] The aux_rd_interval array in struct dc_lttpr_caps is declared with MAX_REPEATER_CNT - 1 (7) elements, indexed 0..6. However, the offset parameter passed to dp_get_eq_aux_rd_interval() can be as large as MAX_REPEATER_CNT (8) when a sink reports 8 LTTPR repeaters via DPCD. This leads to an out-of-bounds read of aux_rd_interval[7] when offset is 8. Fix this by growing aux_rd_interval to MAX_REPEATER_CNT elements to accommodate the full range of valid repeater counts defined by the DP spec. (cherry picked from commit a55a458a8df37a65ffda5cf721d554a8f74f6b04)

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Use krealloc_array() in dal_vector_reserve() [Why & How] dal_vector_reserve() computes the allocation size as "capacity * vector->struct_size" using uint32_t arithmetic, which can silently wrap to a small value on overflow. This would cause krealloc to return a smaller buffer than expected, leading to heap overflows on subsequent vector appends. Replace krealloc() with krealloc_array() which performs an internal overflow check and returns NULL on wrap, preventing the issue. (cherry picked from commit 37668568641ccc4cc1dbca4923d0a16609dd5707)

In the Linux kernel, the following vulnerability has been resolved: vfio/pci: Clean up DMABUFs before disabling function On device shutdown, make vfio_pci_core_close_device() call vfio_pci_dma_buf_cleanup() before the function is disabled via vfio_pci_core_disable(). This ensures that all access via DMABUFs is revoked before the function's BARs become inaccessible. This fixes an issue where, if the function is disabled first, a tiny window exists in which the function's MSE is cleared and yet BARs could still be accessed via the DMABUF. The resources would also be freed and up for grabs by a different driver.