Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO states.c:__clean_func_state() can downgrade scalar zero spill to STACK_ZERO in the following case: *(u64 *)(r10 - 8) = 0; ... checkpoint ... r1 = *(u32 *)(r10 - 4); ... no reads from r10-8 ... Here 4 bytes at r10-8 are dead and verifier changes scalar spill to a combination: 0000pppp (p stands for poison). Such a change breaks precision propagation chains. All places that produce STACK_ZERO should call bpf_mark_chain_precision() for the zero source. This patch fixes the bug in a simplest way possible: avoids converting stack spills of zero to STACK_ZERO. Two smarter approaches are possible: - do bpf_mark_chain_precision() from __clean_func_state() - check slot liveness information in check_stack_write_fixed_off() I investigated both and the changes required are a bit tricky, hence go with a simple fix for the time being.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected be23266b4a08540aa43d8503a2ea10247c8daebe before 436fa689630b741a77ef8c4a6f426479affd5bac; affected be23266b4a08540aa43d8503a2ea10247c8daebe before 2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e |
| Linux / Linux | affected 7.1; unaffected 0 before 7.1; unaffected 7.2.7 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.