"value":"In the Linux kernel, the following vulnerability has been resolved:\n\nworkqueue: Fix spruious data race in __flush_work()\n\nWhen flushing a work item for cancellation, __flush_work() knows that it\nexclusively owns the work item through its PENDING bit. 134874e2eee9\n(\"workqueue: Allow cancel_work_sync() and disable_work() from atomic\ncontexts on BH work items\") added a read of @work->data to determine whether\nto use busy wait for BH work items that are being canceled. While the read\nis safe when @from_cancel, @work->data was read before testing @from_cancel\nto simplify code structure:\n\n\tdata = *work_data_bits(work);\n\tif (from_cancel &&\n\t !WARN_ON_ONCE(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_BH)) {\n\nWhile the read data was never used if !@from_cancel, this could trigger\nKCSAN data race detection spuriously:\n\n ==================================================================\n BUG: KCSAN: data-race in __flush_work / __flush_work\n\n write to 0xffff8881223aa3e8 of 8 bytes by task 3998 on cpu 0:\n instrument_write include/linux/instrumented.h:41 [inline]\n ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline]\n insert_wq_barrier kernel/workqueue.c:3790 [inline]\n start_flush_work kernel/workqueue.c:4142 [inline]\n __flush_work+0x30b/0x570 kernel/workqueue.c:4178\n flush_work kernel/workqueue.c:4229 [inline]\n ...\n\n read to 0xffff8881223aa3e8 of 8 bytes by task 50 on cpu 1:\n __flush_work+0x42a/0x570 kernel/workqueue.c:4188\n flush_work kernel/workqueue.c:4229 [inline]\n flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251\n ...\n\n value changed: 0x0000000000400000 -> 0xffff88810006c00d\n\nReorganize the code so that @from_cancel is tested before @work->data is\naccessed. The only problem is triggering KCSAN detection spuriously. This\nshouldn't need READ_ONCE() or other access qualifiers.\n\nNo functional changes."
"value":"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: workqueue: Fix spruious data race in __flush_work() Al vaciar un elemento de trabajo para su cancelaci\u00f3n, __flush_work() sabe que posee exclusivamente el elemento de trabajo a trav\u00e9s de su bit PENDING. 134874e2eee9 (\"workqueue: Allow cancel_work_sync() and disable_work() from atomic contexts on BH work items\") agreg\u00f3 una lectura de @work->data para determinar si se debe usar la espera activa para los elementos de trabajo de BH que se est\u00e1n cancelando. Si bien la lectura es segura cuando @from_cancel, @work->data se ley\u00f3 antes de probar @from_cancel para simplificar la estructura del c\u00f3digo: data = *work_data_bits(work); if (from_cancel && !WARN_ON_ONCE(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_BH)) { Si bien los datos le\u00eddos nunca se usaron si !@from_cancel, esto podr\u00eda activar la detecci\u00f3n de ejecuci\u00f3n de datos de KCSAN de manera espuria: ====================================================================== ERROR: KCSAN: carrera de datos en __flush_work / __flush_work escribe en 0xffff8881223aa3e8 de 8 bytes por la tarea 3998 en la CPU 0: instrument_write include/linux/instrumented.h:41 [en l\u00ednea] ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [en l\u00ednea] insert_wq_barrier kernel/workqueue.c:3790 [en l\u00ednea] start_flush_work kernel/workqueue.c:4142 [en l\u00ednea] __flush_work+0x30b/0x570 kernel/workqueue.c:4178 flush_work kernel/workqueue.c:4229 [en l\u00ednea] ... le\u00eddo hasta 0xffff8881223aa3e8 de 8 bytes por la tarea 50 en la CPU 1: __flush_work+0x42a/0x570 kernel/workqueue.c:4188 flush_work kernel/workqueue.c:4229 [en l\u00ednea] flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251 ... valor cambiado: 0x0000000000400000 -> 0xffff88810006c00d Reorganice el c\u00f3digo para que @from_cancel se pruebe antes de acceder a @work->data. El \u00fanico problema es que se activa la detecci\u00f3n de KCSAN de manera espuria. Esto no deber\u00eda necesitar READ_ONCE() ni otros calificadores de acceso. No hay cambios funcionales."
