CVE-2024-50140

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: sched/core: Deshabilitar la asignación de páginas en task_tick_mm_cid() Con KASAN y PREEMPT_RT habilitados, llamar a task_work_add() en task_tick_mm_cid() puede causar el siguiente splat. [ 63.696416] ERROR: función inactiva llamada desde un contexto no válido en kernel/locking/spinlock_rt.c:48 [ 63.696416] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 610, name: modprobe [ 63.696416] preempt_count: 10001, esperado: 0 [ 63.696416] Profundidad de anidación de RCU: 1, esperado: 1 Este problema es causado por el siguiente seguimiento de llamada. sched_tick() [ adquirir rq->__lock ] -> task_tick_mm_cid() -> task_work_add() -> __kasan_record_aux_stack() -> kasan_save_stack() -> stack_depot_save_flags() -> alloc_pages_mpol_noprof() -> __alloc_pages_noprof() -> get_page_from_freelist() -> rmqueue() -> rmqueue_pcplist() -> __rmqueue_pcplist() -> rmqueue_bulk() -> rt_spin_lock() El bloqueo rq es un raw_spinlock_t. No podemos dormir mientras lo mantenemos. Es decir, no podemos llamar a alloc_pages() en stack_depot_save_flags(). La función task_tick_mm_cid() con su llamada task_work_add() fue introducida por el commit 223baf9d17f2 ("sched: Fix performance regression presented by mm_cid") en el kernel v6.4. Afortunadamente, hay una variante kasan_record_aux_stack_noalloc() que llama a stack_depot_save_flags() pero no le permite asignar nuevas páginas. Para permitir que task_tick_mm_cid() use task_work sin asignación de páginas, se agrega un nuevo indicador TWAF_NO_ALLOC para habilitar la llamada a kasan_record_aux_stack_noalloc() en lugar de kasan_record_aux_stack() si está configurado. La función task_tick_mm_cid() se modifica para agregar este nuevo indicador. La posible desventaja es la falta de seguimiento de pila en un informe KASAN debido a la nueva asignación de página requerida cuando se llama a task_work_add_noallloc(), lo que debería ser poco común.

In the Linux kernel, the following vulnerability has been resolved: sched/core: Disable page allocation in task_tick_mm_cid() With KASAN and PREEMPT_RT enabled, calling task_work_add() in task_tick_mm_cid() may cause the following splat. [ 63.696416] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 [ 63.696416] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 610, name: modprobe [ 63.696416] preempt_count: 10001, expected: 0 [ 63.696416] RCU nest depth: 1, expected: 1 This problem is caused by the following call trace. sched_tick() [ acquire rq->__lock ] -> task_tick_mm_cid() -> task_work_add() -> __kasan_record_aux_stack() -> kasan_save_stack() -> stack_depot_save_flags() -> alloc_pages_mpol_noprof() -> __alloc_pages_noprof() -> get_page_from_freelist() -> rmqueue() -> rmqueue_pcplist() -> __rmqueue_pcplist() -> rmqueue_bulk() -> rt_spin_lock() The rq lock is a raw_spinlock_t. We can't sleep while holding it. IOW, we can't call alloc_pages() in stack_depot_save_flags(). The task_tick_mm_cid() function with its task_work_add() call was introduced by commit 223baf9d17f2 ("sched: Fix performance regression introduced by mm_cid") in v6.4 kernel. Fortunately, there is a kasan_record_aux_stack_noalloc() variant that calls stack_depot_save_flags() while not allowing it to allocate new pages. To allow task_tick_mm_cid() to use task_work without page allocation, a new TWAF_NO_ALLOC flag is added to enable calling kasan_record_aux_stack_noalloc() instead of kasan_record_aux_stack() if set. The task_tick_mm_cid() function is modified to add this new flag. The possible downside is the missing stack trace in a KASAN report due to new page allocation required when task_work_add_noallloc() is called which should be rare.

Attila Szász discovered that the HFS+ file system implementation in the Linux Kernel contained a heap overflow vulnerability. An attacker could use a specially crafted file system image that, when mounted, could cause a denial of service or possibly execute arbitrary code. Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system.