CVE-2026-63830

Description

In the Linux kernel, the following vulnerability has been resolved: net: skmsg: preserve sg.copy across SG transforms The sk_msg sg.copy bitmap is part of the scatterlist entry ownership state. A set bit tells sk_msg_compute_data_pointers() not to expose the entry through writable BPF ctx->data. This protects entries backed by pages that are not private to the sk_msg, such as splice-backed file page-cache pages. Several sk_msg transform paths move, copy, split, or compact msg->sg.data[] entries without moving the matching sg.copy bit. This can make an externally backed entry arrive at a new slot with a clear copy bit. A later SK_MSG verdict can then expose sg_virt(sge) as writable ctx->data and BPF stores can modify the original page cache. Keep sg.copy synchronized with sg.data[] whenever entries are transferred, shifted, split, or copied into a new sk_msg. Clear the bit when an entry is replaced by a newly allocated private page or freed. This covers the BPF pull/push/pop helpers, sk_msg_shift_left/right(), sk_msg_xfer(), and tls_split_open_record(), including the partial tail entry created during TLS open-record splitting.

References

• https://git.kernel.org/stable/c/0eb4c16c4adb262763bda870a8ed38a1a9dec7ec
• https://git.kernel.org/stable/c/1acdd14c0990dd1cd4b6534f00366d2e6dfce05f
• https://git.kernel.org/stable/c/21ed9540a8e1906dfcbc1bb82ba9b4de4fa4bd6d
• https://git.kernel.org/stable/c/406e8a651a7b854c41fecd5117bb282b3a6c2c6b
• https://git.kernel.org/stable/c/9bb86d8184b37503816150c4a6ad3c17dfdbe827