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.
References
Configurations
Configuration 1 (hide)
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History
31 Oct 2024, 14:16
Type | Values Removed | Values Added |
---|---|---|
CPE | cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.16:rc5:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:* |
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CVSS |
v2 : v3 : |
v2 : unknown
v3 : 5.5 |
First Time |
Linux
Linux linux Kernel |
|
CWE | NVD-CWE-noinfo | |
References | () https://git.kernel.org/stable/c/423628125a484538111c2c6d9bb1588eb086053b - Patch | |
References | () https://git.kernel.org/stable/c/7d3baf0afa3aa9102d6a521a8e4c41888bb79882 - Patch |
20 Jun 2024, 12:43
Type | Values Removed | Values Added |
---|---|---|
Summary |
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19 Jun 2024, 15:15
Type | Values Removed | Values Added |
---|---|---|
New CVE |
Information
Published : 2024-06-19 15:15
Updated : 2024-10-31 14:16
NVD link : CVE-2021-47608
Mitre link : CVE-2021-47608
CVE.ORG link : CVE-2021-47608
JSON object : View
Products Affected
linux
- linux_kernel
CWE