CVE-2026-53078

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/18e3ffde1822f0b48b1753bf34aa97ce839df1d8
• https://git.kernel.org/stable/c/10f86a2a5c91fc4c4d001960f1c21abe52545ef6

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