bpf: Drop scalar id on sign-extending narrowing stack fills
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 7.2.6
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Drop scalar id on sign-extending narrowing stack fills When a spilled scalar is filled back with a sign-extending narrowing load (BPF_MEMSX), check_stack_read_fixed_off() copies the spilled register including its scalar id, but coerce_reg_to_size_sx() then sign-extends the filled register's value. If the same slot is also filled with a plain zero-extending load (BPF_MEM), both destination registers share the id yet hold different values. A later 'if <zext-reg> == const' then refines the sign-extended register through sync_linked_regs() to a value it does not have at runtime (e.g. the verifier believes 0x80000000 while the register is 0xffffffff80000000), which can be turned into an out-of-bounds access. Drop the shared scalar id at the sign-extension site in check_mem_access() when sign extension actually changes the value, mirroring the BPF_MOVSX handling in check_alu_op() (no_sext = reg_umax < 2^(size*8-1)).
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From 3cd5c890652ba1f0682adc291b5446245259b692 · fixed in f3614622dc41f3dd99bb4f691da253814e4e6cae; From 3cd5c890652ba1f0682adc291b5446245259b692 · fixed in 2cb5f4ca695ebe552647e5ba4aad6934d6a43bae
- Linux Linux
7.0
- KernelLinux
From 7.0.0 · fixed in 7.2.6