CVE-2024-26796

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: controladores: perf: ctr_get_width la función para legado no está definida Con los parámetros CONFIG_RISCV_PMU_LEGACY=y y CONFIG_RISCV_PMU_SBI=n el kernel de Linux falla cuando intenta el registro de rendimiento: $ perf record ls [ 46.749286] No se puede manejar la desreferencia del puntero NULL del kernel en la dirección virtual 0000000000000000 [ 46.750199] Ups [#1] [ 46.750342] Módulos vinculados en: [ 46.750608] CPU: 0 PID: 107 Comm: perf-exec Not tainted 6.6.0 #2 [ 46.750906] Nombre del hardware : riscv-virtio,qemu (DT) [ 46.751184] epc : 0x0 [ 46.751430 ] ra : arch_perf_update_userpage+0x54/0x13e [ 46.751680] epc : 00000000000000000 ra : ffffffff8072ee52 sp : ff20000 00022b8f0 [46.751958] gp: ffffffff81505988 tp: ff6000000290d400 t0: ff2000000022b9c0 [ 46.752229] t1 : 0000000000000001 t2 : 0000000000000003 s0 : ff2000000022b930 [ 46.752451] s1 : ff600000028fb000 a0 : 0000000000000000 a 1: ff600000028fb000 [46.752673] a2: 0000000ae2751268 a3: 00000000004fb708 a4: 00000000000000004 [46.752895] a5: 0000000000000000 a6: 000000000017ffe3 a7: 00000000000000d2 [46.753117] s2: ff600000028fb000 s3: 0000000ae2751268 s4: 0000000000000000 [46.753338] s5: ffffffff8153e290 s6: ff600000863b9000 s7: ff60000002 961078 [46.753562] s8: ff60000002961048 s9: ff60000002961058 s10: 00000000000000001 [46.753783] s11: 0000000000000018 t3: ffffffffffffff ff t4 : ffffffffffffffff [ 46.754005] t5 : ff6000000292270c t6: ff2000000022bb30 [46.754179] estado: 0000000200000100 badaddr: 00000000000000000 causa: 0000000000000000c [46.754653] Código: No se puede acceder instrucción en 0xffffffffffffffec. [ 46.754939] ---[ end trace 0000000000000000 ]--- [ 46.755131] nota: perf-exec[107] salió con irqs deshabilitados [ 46.755546] nota: perf-exec[107] salió con preempt_count 4 Esto sucede porque en el legado En este caso, la función ctr_get_width no se definió, pero se usa en arch_perf_update_userpage. También elimine el control adicional en riscv_pmu_ctr_get_width_mask

In the Linux kernel, the following vulnerability has been resolved: drivers: perf: ctr_get_width function for legacy is not defined With parameters CONFIG_RISCV_PMU_LEGACY=y and CONFIG_RISCV_PMU_SBI=n linux kernel crashes when you try perf record: $ perf record ls [ 46.749286] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 46.750199] Oops [#1] [ 46.750342] Modules linked in: [ 46.750608] CPU: 0 PID: 107 Comm: perf-exec Not tainted 6.6.0 #2 [ 46.750906] Hardware name: riscv-virtio,qemu (DT) [ 46.751184] epc : 0x0 [ 46.751430] ra : arch_perf_update_userpage+0x54/0x13e [ 46.751680] epc : 0000000000000000 ra : ffffffff8072ee52 sp : ff2000000022b8f0 [ 46.751958] gp : ffffffff81505988 tp : ff6000000290d400 t0 : ff2000000022b9c0 [ 46.752229] t1 : 0000000000000001 t2 : 0000000000000003 s0 : ff2000000022b930 [ 46.752451] s1 : ff600000028fb000 a0 : 0000000000000000 a1 : ff600000028fb000 [ 46.752673] a2 : 0000000ae2751268 a3 : 00000000004fb708 a4 : 0000000000000004 [ 46.752895] a5 : 0000000000000000 a6 : 000000000017ffe3 a7 : 00000000000000d2 [ 46.753117] s2 : ff600000028fb000 s3 : 0000000ae2751268 s4 : 0000000000000000 [ 46.753338] s5 : ffffffff8153e290 s6 : ff600000863b9000 s7 : ff60000002961078 [ 46.753562] s8 : ff60000002961048 s9 : ff60000002961058 s10: 0000000000000001 [ 46.753783] s11: 0000000000000018 t3 : ffffffffffffffff t4 : ffffffffffffffff [ 46.754005] t5 : ff6000000292270c t6 : ff2000000022bb30 [ 46.754179] status: 0000000200000100 badaddr: 0000000000000000 cause: 000000000000000c [ 46.754653] Code: Unable to access instruction at 0xffffffffffffffec. [ 46.754939] ---[ end trace 0000000000000000 ]--- [ 46.755131] note: perf-exec[107] exited with irqs disabled [ 46.755546] note: perf-exec[107] exited with preempt_count 4 This happens because in the legacy case the ctr_get_width function was not defined, but it is used in arch_perf_update_userpage. Also remove extra check in riscv_pmu_ctr_get_width_mask