atm: Fix NULL pointer dereference

In the Linux kernel, the following vulnerability has been resolved: atm: Fix NULL pointer dereference When MPOA_cache_impos_rcvd() receives the msg, it can trigger Null Pointer Dereference Vulnerability if both entry and holding_time are NULL. Because there is only for the situation where entry is NULL and holding_time exists, it can be passed when both entry and holding_time are NULL. If these are NULL, the entry will be passd to eg_cache_put() as parameter and it is referenced by entry->use code in it. kasan log: [ 3.316691] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006:I [ 3.317568] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 3.318188] CPU: 3 UID: 0 PID: 79 Comm: ex Not tainted 6.14.0-rc2 #102 [ 3.318601] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 [ 3.319298] RIP: 0010:eg_cache_remove_entry+0xa5/0x470 [ 3.319677] Code: c1 f7 6e fd 48 c7 c7 00 7e 38 b2 e8 95 64 54 fd 48 c7 c7 40 7e 38 b2 48 89 ee e80 [ 3.321220] RSP: 0018:ffff88800583f8a8 EFLAGS: 00010006 [ 3.321596] RAX: 0000000000000006 RBX: ffff888005989000 RCX: ffffffffaecc2d8e [ 3.322112] RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000030 [ 3.322643] RBP: 0000000000000000 R08: 0000000000000000 R09: fffffbfff6558b88 [ 3.323181] R10: 0000000000000003 R11: 203a207972746e65 R12: 1ffff11000b07f15 [ 3.323707] R13: dffffc0000000000 R14: ffff888005989000 R15: ffff888005989068 [ 3.324185] FS: 000000001b6313c0(0000) GS:ffff88806d380000(0000) knlGS:0000000000000000 [ 3.325042] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3.325545] CR2: 00000000004b4b40 CR3: 000000000248e000 CR4: 00000000000006f0 [ 3.326430] Call Trace: [ 3.326725] <TASK> [ 3.326927] ? die_addr+0x3c/0xa0 [ 3.327330] ? exc_general_protection+0x161/0x2a0 [ 3.327662] ? asm_exc_general_protection+0x26/0x30 [ 3.328214] ? vprintk_emit+0x15e/0x420 [ 3.328543] ? eg_cache_remove_entry+0xa5/0x470 [ 3.328910] ? eg_cache_remove_entry+0x9a/0x470 [ 3.329294] ? __pfx_eg_cache_remove_entry+0x10/0x10 [ 3.329664] ? console_unlock+0x107/0x1d0 [ 3.329946] ? __pfx_console_unlock+0x10/0x10 [ 3.330283] ? do_syscall_64+0xa6/0x1a0 [ 3.330584] ? entry_SYSCALL_64_after_hwframe+0x47/0x7f [ 3.331090] ? __pfx_prb_read_valid+0x10/0x10 [ 3.331395] ? down_trylock+0x52/0x80 [ 3.331703] ? vprintk_emit+0x15e/0x420 [ 3.331986] ? __pfx_vprintk_emit+0x10/0x10 [ 3.332279] ? down_trylock+0x52/0x80 [ 3.332527] ? _printk+0xbf/0x100 [ 3.332762] ? __pfx__printk+0x10/0x10 [ 3.333007] ? _raw_write_lock_irq+0x81/0xe0 [ 3.333284] ? __pfx__raw_write_lock_irq+0x10/0x10 [ 3.333614] msg_from_mpoad+0x1185/0x2750 [ 3.333893] ? __build_skb_around+0x27b/0x3a0 [ 3.334183] ? __pfx_msg_from_mpoad+0x10/0x10 [ 3.334501] ? __alloc_skb+0x1c0/0x310 [ 3.334809] ? __pfx___alloc_skb+0x10/0x10 [ 3.335283] ? _raw_spin_lock+0xe0/0xe0 [ 3.335632] ? finish_wait+0x8d/0x1e0 [ 3.335975] vcc_sendmsg+0x684/0xba0 [ 3.336250] ? __pfx_vcc_sendmsg+0x10/0x10 [ 3.336587] ? __pfx_autoremove_wake_function+0x10/0x10 [ 3.337056] ? fdget+0x176/0x3e0 [ 3.337348] __sys_sendto+0x4a2/0x510 [ 3.337663] ? __pfx___sys_sendto+0x10/0x10 [ 3.337969] ? ioctl_has_perm.constprop.0.isra.0+0x284/0x400 [ 3.338364] ? sock_ioctl+0x1bb/0x5a0 [ 3.338653] ? __rseq_handle_notify_resume+0x825/0xd20 [ 3.339017] ? __pfx_sock_ioctl+0x10/0x10 [ 3.339316] ? __pfx___rseq_handle_notify_resume+0x10/0x10 [ 3.339727] ? selinux_file_ioctl+0xa4/0x260 [ 3.340166] __x64_sys_sendto+0xe0/0x1c0 [ 3.340526] ? syscall_exit_to_user_mode+0x123/0x140 [ 3.340898] do_syscall_64+0xa6/0x1a0 [ 3.341170] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 3.341533] RIP: 0033:0x44a380 [ 3.341757] Code: 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 41 89 ca 64 8b 04 25 18 00 00 00 85 c00 [ ---truncated---

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于MPOA_cache_impos_rcvd函数空指针取消引用。

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