SUSE: CVE-2021-47608: SUSE Linux Security Advisory
Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix kernel address leakage in atomic fetch The change in commit 37086bfdc737 ("bpf: Propagate stack bounds to registers in atomics w/ BPF_FETCH") around check_mem_access() handling is buggy since this would allow for unprivileged users to leak kernel pointers. For example, an atomic fetch/and with -1 on a stack destination which holds a spilled pointer will migrate the spilled register type into a scalar, which can then be exported out of the program (since scalar != pointer) by dumping it into a map value. The original implementation of XADD was preventing this situation by using a double call to check_mem_access() one with BPF_READ and a subsequent one with BPF_WRITE, in both cases passing -1 as a placeholder value instead of register as per XADD semantics since it didn't contain a value fetch. The BPF_READ also included a check in check_stack_read_fixed_off() which rejects the program if the stack slot is of __is_pointer_value() if dst_regno < 0. The latter is to distinguish whether we're dealing with a regular stack spill/ fill or some arithmetical operation which is disallowed on non-scalars, see also 6e7e63cbb023 ("bpf: Forbid XADD on spilled pointers for unprivileged users") for more context on check_mem_access() and its handling of placeholder value -1. One minimally intrusive option to fix the leak is for the BPF_FETCH case to initially check the BPF_READ case via check_mem_access() with -1 as register, followed by the actual load case with non-negative load_reg to propagate stack bounds to registers.
Solution(s)
- suse-upgrade-cluster-md-kmp-azure
- suse-upgrade-cluster-md-kmp-rt
- suse-upgrade-dlm-kmp-azure
- suse-upgrade-dlm-kmp-rt
- suse-upgrade-gfs2-kmp-azure
- suse-upgrade-gfs2-kmp-rt
- suse-upgrade-kernel-azure
- suse-upgrade-kernel-azure-devel
- suse-upgrade-kernel-azure-extra
- suse-upgrade-kernel-azure-livepatch-devel
- suse-upgrade-kernel-azure-optional
- suse-upgrade-kernel-azure-vdso
- suse-upgrade-kernel-devel-azure
- suse-upgrade-kernel-devel-rt
- suse-upgrade-kernel-rt
- suse-upgrade-kernel-rt-devel
- suse-upgrade-kernel-rt-extra
- suse-upgrade-kernel-rt-livepatch
- suse-upgrade-kernel-rt-livepatch-devel
- suse-upgrade-kernel-rt-optional
- suse-upgrade-kernel-rt-vdso
- suse-upgrade-kernel-rt_debug
- suse-upgrade-kernel-rt_debug-devel
- suse-upgrade-kernel-rt_debug-livepatch-devel
- suse-upgrade-kernel-rt_debug-vdso
- suse-upgrade-kernel-source-azure
- suse-upgrade-kernel-source-rt
- suse-upgrade-kernel-syms-azure
- suse-upgrade-kernel-syms-rt
- suse-upgrade-kselftests-kmp-azure
- suse-upgrade-kselftests-kmp-rt
- suse-upgrade-ocfs2-kmp-azure
- suse-upgrade-ocfs2-kmp-rt
- suse-upgrade-reiserfs-kmp-azure
- suse-upgrade-reiserfs-kmp-rt
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