CVE-2026-53078

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix same-register dst/src OOB read and pointer leak in sock_ops

When a BPF sock_ops program accesses ctx fields with dst_reg == src_reg,

the SOCK_OPS_GET_SK() and SOCK_OPS_GET_FIELD() macros fail to zero the

destination register in the !fullsock / !locked_tcp_sock path.

Both macros borrow a temporary register to check is_fullsock /

is_locked_tcp_sock when dst_reg == src_reg, because dst_reg holds the

ctx pointer. When the check is false (e.g., TCP_NEW_SYN_RECV state with

a request_sock), dst_reg should be zeroed but is not, leaving the stale

ctx pointer:

- SOCK_OPS_GET_SK: dst_reg retains the ctx pointer, passes NULL checks

as PTR_TO_SOCKET_OR_NULL, and can be used as a bogus socket pointer,

leading to stack-out-of-bounds access in helpers like

bpf_skc_to_tcp6_sock().

- SOCK_OPS_GET_FIELD: dst_reg retains the ctx pointer which the

verifier believes is a SCALAR_VALUE, leaking a kernel pointer.

Fix both macros by:

- Changing JMP_A(1) to JMP_A(2) in the fullsock path to skip the

added instruction.

- Adding BPF_MOV64_IMM(si->dst_reg, 0) after the temp register

restore in the !fullsock path, placed after the restore because

dst_reg == src_reg means we need src_reg intact to read ctx->temp.