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In the Linux kernel, the following vulnerability has been resolved: vdpa/mlx5: Fix invalid mr resource destroy Certain error paths from mlx5_vdpa_dev_add() can end up releasing mr resources which never got initialized in the first place. This patch adds the missing check in mlx5_vdpa_destroy_mr_resources() to block releasing non-initialized mr resources. Reference trace: mlx5_core 0000:08:00.2: mlx5_vdpa_dev_add:3274:(pid 2700) warning: No mac address provisioned? BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 140216067 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 8 PID: 2700 Comm: vdpa Kdump: loaded Not tainted 5.14.0-496.el9.x86_64 #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:vhost_iotlb_del_range+0xf/0xe0 [vhost_iotlb] Code: [...] RSP: 0018:ff1c823ac23077f0 EFLAGS: 00010246 RAX: ffffffffc1a21a60 RBX: ffffffff899567a0 RCX: 0000000000000000 RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000000000000000 RBP: ff1bda1f7c21e800 R08: 0000000000000000 R09: ff1c823ac2307670 R10: ff1c823ac2307668 R11: ffffffff8a9e7b68 R12: 0000000000000000 R13: 0000000000000000 R14: ff1bda1f43e341a0 R15: 00000000ffffffea FS: 00007f56eba7c740(0000) GS:ff1bda269f800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000104d90001 CR4: 0000000000771ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: ? show_trace_log_lvl+0x1c4/0x2df ? show_trace_log_lvl+0x1c4/0x2df ? mlx5_vdpa_free+0x3d/0x150 [mlx5_vdpa] ? __die_body.cold+0x8/0xd ? page_fault_oops+0x134/0x170 ? __irq_work_queue_local+0x2b/0xc0 ? irq_work_queue+0x2c/0x50 ? exc_page_fault+0x62/0x150 ? asm_exc_page_fault+0x22/0x30 ? __pfx_mlx5_vdpa_free+0x10/0x10 [mlx5_vdpa] ? vhost_iotlb_del_range+0xf/0xe0 [vhost_iotlb] mlx5_vdpa_free+0x3d/0x150 [mlx5_vdpa] vdpa_release_dev+0x1e/0x50 [vdpa] device_release+0x31/0x90 kobject_cleanup+0x37/0x130 mlx5_vdpa_dev_add+0x2d2/0x7a0 [mlx5_vdpa] vdpa_nl_cmd_dev_add_set_doit+0x277/0x4c0 [vdpa] genl_family_rcv_msg_doit+0xd9/0x130 genl_family_rcv_msg+0x14d/0x220 ? __pfx_vdpa_nl_cmd_dev_add_set_doit+0x10/0x10 [vdpa] ? _copy_to_user+0x1a/0x30 ? move_addr_to_user+0x4b/0xe0 genl_rcv_msg+0x47/0xa0 ? __import_iovec+0x46/0x150 ? __pfx_genl_rcv_msg+0x10/0x10 netlink_rcv_skb+0x54/0x100 genl_rcv+0x24/0x40 netlink_unicast+0x245/0x370 netlink_sendmsg+0x206/0x440 __sys_sendto+0x1dc/0x1f0 ? do_read_fault+0x10c/0x1d0 ? do_pte_missing+0x10d/0x190 __x64_sys_sendto+0x20/0x30 do_syscall_64+0x5c/0xf0 ? __count_memcg_events+0x4f/0xb0 ? mm_account_fault+0x6c/0x100 ? handle_mm_fault+0x116/0x270 ? do_user_addr_fault+0x1d6/0x6a0 ? do_syscall_64+0x6b/0xf0 ? clear_bhb_loop+0x25/0x80 ? clear_bhb_loop+0x25/0x80 ? clear_bhb_loop+0x25/0x80 ? clear_bhb_loop+0x25/0x80 ? clear_bhb_loop+0x25/0x80 entry_SYSCALL_64_after_hwframe+0x78/0x80
CVSS 3.1 Base Score 5.5. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Here, a boolean initiailized field is consulted to ensure that initialization tasks are only completed once. However, the field is mistakenly set to true during static initialization, so the initialization code is never reached.
}
initialized = true;// perform initialization tasksThe following code intends to limit certain operations to the administrator only.
}$uid = ExtractUserID($state);# do stuffDoAdminThings();If the application is unable to extract the state information - say, due to a database timeout - then the $uid variable will not be explicitly set by the programmer. This will cause $uid to be regarded as equivalent to "0" in the conditional, allowing the original user to perform administrator actions. Even if the attacker cannot directly influence the state data, unexpected errors could cause incorrect privileges to be assigned to a user just by accident.
The following code intends to concatenate a string to a variable and print the string.
printf("%s", str);This might seem innocent enough, but str was not initialized, so it contains random memory. As a result, str[0] might not contain the null terminator, so the copy might start at an offset other than 0. The consequences can vary, depending on the underlying memory.
If a null terminator is found before str[8], then some bytes of random garbage will be printed before the "hello world" string. The memory might contain sensitive information from previous uses, such as a password (which might occur as a result of CWE-14 or CWE-244). In this example, it might not be a big deal, but consider what could happen if large amounts of memory are printed out before the null terminator is found.
If a null terminator isn't found before str[8], then a buffer overflow could occur, since strcat will first look for the null terminator, then copy 12 bytes starting with that location. Alternately, a buffer over-read might occur (CWE-126) if a null terminator isn't found before the end of the memory segment is reached, leading to a segmentation fault and crash.
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