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      "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix use-after-free in tw_timer_handler\n\nA real world panic issue was found as follow in Linux 5.4.\n\n    BUG: unable to handle page fault for address: ffffde49a863de28\n    PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0\n    RIP: 0010:tw_timer_handler+0x20/0x40\n    Call Trace:\n     \u003cIRQ\u003e\n     call_timer_fn+0x2b/0x120\n     run_timer_softirq+0x1ef/0x450\n     __do_softirq+0x10d/0x2b8\n     irq_exit+0xc7/0xd0\n     smp_apic_timer_interrupt+0x68/0x120\n     apic_timer_interrupt+0xf/0x20\n\nThis issue was also reported since 2017 in the thread [1],\nunfortunately, the issue was still can be reproduced after fixing\nDCCP.\n\nThe ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net\nnamespace is destroyed since tcp_sk_ops is registered befrore\nipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops\nin the list of pernet_list. There will be a use-after-free on\nnet-\u003emib.net_statistics in tw_timer_handler after ipv4_mib_exit_net\nif there are some inflight time-wait timers.\n\nThis bug is not introduced by commit f2bf415cfed7 (\"mib: add net to\nNET_ADD_STATS_BH\") since the net_statistics is a global variable\ninstead of dynamic allocation and freeing. Actually, commit\n61a7e26028b9 (\"mib: put net statistics on struct net\") introduces\nthe bug since it put net statistics on struct net and free it when\nnet namespace is destroyed.\n\nMoving init_ipv4_mibs() to the front of tcp_init() to fix this bug\nand replace pr_crit() with panic() since continuing is meaningless\nwhen init_ipv4_mibs() fails.\n\n[1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1",
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            "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: net: corrige use-after-free en tw_timer_handler Se encontr\u00f3 un problema de p\u00e1nico en el mundo real como se muestra a continuaci\u00f3n en Linux 5.4. ERROR: no se puede manejar el error de p\u00e1gina para la direcci\u00f3n: ffffde49a863de28 PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0 RIP: 0010:tw_timer_handler+0x20/0x40 Seguimiento de llamadas:  call_timer_fn+0x2b/ 0x120 run_timer_softirq+0x1ef/0x450 __do_softirq+0x10d/ 0x2b8 irq_exit+0xc7/0xd0 smp_apic_timer_interrupt+0x68/0x120 apic_timer_interrupt+0xf/0x20 Este problema tambi\u00e9n se inform\u00f3 desde 2017 en el hilo [1], desafortunadamente, el problema a\u00fan se puede reproducir despu\u00e9s de corregir DCCP. ipv4_mib_exit_net se llama antes de tcp_sk_exit_batch cuando se destruye un espacio de nombres de red, ya que tcp_sk_ops est\u00e1 registrado antes de ipv4_mib_ops, lo que significa que tcp_sk_ops est\u00e1 al frente de ipv4_mib_ops en la lista de pernet_list. Habr\u00e1 un use-after-free en net-\u0026gt;mib.net_statistics en tw_timer_handler despu\u00e9s de ipv4_mib_exit_net si hay algunos temporizadores de espera a bordo. Este error no se introduce mediante la confirmaci\u00f3n f2bf415cfed7 (\"mib: add net to NET_ADD_STATS_BH\") ya que net_statistics es una variable global en lugar de una asignaci\u00f3n y liberaci\u00f3n din\u00e1micas. En realidad, la confirmaci\u00f3n 61a7e26028b9 (\"mib: poner estad\u00edsticas de red en struct net\") introduce el error ya que coloca estad\u00edsticas de red en struct net y las libera cuando se destruye el espacio de nombres de red. Mover init_ipv4_mibs() al frente de tcp_init() para corregir este error y reemplazar pr_crit() con p\u00e1nico() ya que continuar no tiene sentido cuando init_ipv4_mibs() falla. [1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1"
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