In the Linux kernel, the following vulnerability has been resolved:
proc/vmcore: fix clearing user buffer by properly using clear_user()
To clear a user buffer we cannot simply use memset, we have to use clear_user(). With a virtio-mem device that registers a vmcore_cb and has some logically unplugged memory inside an added Linux memory block, I can easily trigger a BUG by copying the vmcore via "cp":
systemd[1]: Starting Kdump Vmcore Save Service... kdump[420]: Kdump is using the default log level(3). kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[465]: saving vmcore-dmesg.txt complete kdump[467]: saving vmcore BUG: unable to handle page fault for address: 00007f2374e01000 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Oops: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86 Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81 RSP: 0018:ffffc9000073be08 EFLAGS: 00010212 RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000 RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008 RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Call Trace: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 ksys_read+0x4f/0xc0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae
Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access Prevention (SMAP)", which is used to detect wrong access from the kernel to user buffers like this: SMAP triggers a permissions violation on wrong access. In the x86-64 variant of clear_user(), SMAP is properly handled via clac()+stac().
To fix, properly use clear_user() when we're dealing with a user buffer.
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade bpftoolUpgrade kernel-debuginfo-common-aarch64Upgrade kernel-livepatch-5.10.93-87.444Upgrade perfUpgrade kernel-toolsUpgrade python-perfUpgrade kernel-develUpgrade kernel-tools-develUpgrade kernelUpgrade bpftool-debuginfoUpgrade kernel-livepatch-4.14.262-200.489Upgrade kernel-debuginfo-common-x86_64Upgrade kernel-tools-debuginfoUpgrade perf-debuginfoUpgrade python-perf-debuginfoUpgrade kernel-headersUpgrade kernel-debuginfo | Dec 12, 2024 | May 24, 2024 |
| Debian | — | Upgrade linux | Jul 30, 2024 | May 24, 2024 |
| Huawei Euleros 2_0_sp9 | — | Upgrade kernelUpgrade python3-perfUpgrade kernel-tools-libsUpgrade kernel-tools | Oct 8, 2024 | May 24, 2024 |
| Redhat_linux | — | Upgrade kernelNo solution exists | Sep 25, 2024 | May 24, 2024 |
| Suse | — | Upgrade kernel-azure-vdsoUpgrade kernel-rt_debug-vdsoUpgrade cluster-md-kmp-azureUpgrade kernel-symsUpgrade kernel-default-develUpgrade kernel-default-extraUpgrade ocfs2-kmp-rtUpgrade kernel-syms-azureUpgrade kernel-source-azureUpgrade kernel-default-manUpgrade kernel-docsUpgrade kernel-rt-develUpgrade kernel-rt_debugUpgrade reiserfs-kmp-azureUpgrade kernel-sourceUpgrade kernel-devel-azureUpgrade kernel-devel-rtUpgrade kernel-azure-develUpgrade kernel-macrosUpgrade dlm-kmp-azureUpgrade gfs2-kmp-rtUpgrade kernel-rt-livepatch-develUpgrade kernel-syms-rtUpgrade kernel-rtUpgrade kernel-azure-livepatch-develUpgrade kernel-rt-extraUpgrade kernel-develUpgrade dlm-kmp-rtUpgrade ocfs2-kmp-azureUpgrade cluster-md-kmp-rtUpgrade kernel-azure-extraUpgrade kernel-azure-optionalUpgrade kernel-source-rtUpgrade kernel-rt-vdsoUpgrade kernel-obs-buildUpgrade gfs2-kmp-azureUpgrade kernel-default-baseUpgrade kselftests-kmp-rtUpgrade kernel-rt_debug-livepatch-develUpgrade kernel-rt-optionalUpgrade kernel-defaultUpgrade kernel-rt-livepatchUpgrade kernel-azure-baseUpgrade kernel-azureUpgrade kselftests-kmp-azureUpgrade kernel-rt_debug-develUpgrade reiserfs-kmp-rt | Aug 9, 2024 | May 24, 2024 |
| Ubuntu | — | Upgrade linux-gcp-fipsUpgrade linux-oracle-5.4Upgrade linux-hwe-5.4Upgrade linux-aws-fipsUpgrade linuxUpgrade linux-awsUpgrade linux-ibm-5.4Upgrade linux-azure-fipsUpgrade linux-gcpUpgrade linux-gcp-5.4Upgrade linux-gkeopUpgrade linux-bluefieldUpgrade linux-gcp-4.15Upgrade linux-ibmUpgrade linux-aws-5.4Upgrade linux-azure-4.15Upgrade linux-raspiUpgrade linux-azureUpgrade linux-raspi-5.4Upgrade linux-aws-hweUpgrade linux-fipsUpgrade linux-oracleUpgrade linux-azure-5.4Upgrade linux-hweUpgrade linux-kvm | Nov 19, 2024 | May 24, 2024 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Jan 20, 2025 | May 24, 2024 |
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