Описание
In the Linux kernel, the following vulnerability has been resolved:
bpf: Explicitly check accesses to bpf_sock_addr
Syzkaller found a kernel warning on the following sock_addr program:
0: r0 = 0
1: r2 = *(u32 *)(r1 +60)
2: exit
which triggers:
verifier bug: error during ctx access conversion (0)
This is happening because offset 60 in bpf_sock_addr corresponds to an
implicit padding of 4 bytes, right after msg_src_ip4. Access to this
padding isn't rejected in sock_addr_is_valid_access and it thus later
fails to convert the access.
This patch fixes it by explicitly checking the various fields of
bpf_sock_addr in sock_addr_is_valid_access.
I checked the other ctx structures and is_valid_access functions and
didn't find any other similar cases. Other cases of (properly handled)
padding are covered in new tests in a subsequent patch.
A vulnerability was discovered in the Linux kernel’s Berkeley Packet Filter (BPF) subsystem related to insufficient access validation in the sock_addr context. The BPF verifier did not explicitly reject access to a 4-byte implicit padding following the msg_src_ip4 field within the bpf_sock_addr structure. Syzkaller, a kernel testing and fuzzing tool, identified a kernel warning triggered when a BPF program attempted to read from this padding, revealing that the sock_addr_is_valid_access function did not enforce a complete set of bounds checks. A patch has been applied upstream to explicitly validate all relevant fields and prevent out-of-bounds access.
Меры по смягчению последствий
To mitigate this issue, restrict unprivileged users from loading BPF programs by setting kernel.unprivileged_bpf_disabled to 1. This can be achieved by running sysctl -w kernel.unprivileged_bpf_disabled=1 or by adding kernel.unprivileged_bpf_disabled = 1 to /etc/sysctl.d/99-sysctl.conf and applying with sysctl -p. This may affect applications that utilize unprivileged BPF. A system reboot may be required.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred |
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Дополнительная информация
Статус:
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: bpf: Explicitly check accesses to bpf_sock_addr Syzkaller found a kernel warning on the following sock_addr program: 0: r0 = 0 1: r2 = *(u32 *)(r1 +60) 2: exit which triggers: verifier bug: error during ctx access conversion (0) This is happening because offset 60 in bpf_sock_addr corresponds to an implicit padding of 4 bytes, right after msg_src_ip4. Access to this padding isn't rejected in sock_addr_is_valid_access and it thus later fails to convert the access. This patch fixes it by explicitly checking the various fields of bpf_sock_addr in sock_addr_is_valid_access. I checked the other ctx structures and is_valid_access functions and didn't find any other similar cases. Other cases of (properly handled) padding are covered in new tests in a subsequent patch.
In the Linux kernel, the following vulnerability has been resolved: bpf: Explicitly check accesses to bpf_sock_addr Syzkaller found a kernel warning on the following sock_addr program: 0: r0 = 0 1: r2 = *(u32 *)(r1 +60) 2: exit which triggers: verifier bug: error during ctx access conversion (0) This is happening because offset 60 in bpf_sock_addr corresponds to an implicit padding of 4 bytes, right after msg_src_ip4. Access to this padding isn't rejected in sock_addr_is_valid_access and it thus later fails to convert the access. This patch fixes it by explicitly checking the various fields of bpf_sock_addr in sock_addr_is_valid_access. I checked the other ctx structures and is_valid_access functions and didn't find any other similar cases. Other cases of (properly handled) padding are covered in new tests in a subsequent patch.
In the Linux kernel, the following vulnerability has been resolved: b ...
In the Linux kernel, the following vulnerability has been resolved: bpf: Explicitly check accesses to bpf_sock_addr Syzkaller found a kernel warning on the following sock_addr program: 0: r0 = 0 1: r2 = *(u32 *)(r1 +60) 2: exit which triggers: verifier bug: error during ctx access conversion (0) This is happening because offset 60 in bpf_sock_addr corresponds to an implicit padding of 4 bytes, right after msg_src_ip4. Access to this padding isn't rejected in sock_addr_is_valid_access and it thus later fails to convert the access. This patch fixes it by explicitly checking the various fields of bpf_sock_addr in sock_addr_is_valid_access. I checked the other ctx structures and is_valid_access functions and didn't find any other similar cases. Other cases of (properly handled) padding are covered in new tests in a subsequent patch.
5.5 Medium
CVSS3