net: bridge: avoid recursive multicast port cleanup

Overview

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

net: bridge: avoid recursive multicast port cleanup

br_multicast_sg_del_exclude_ports() removes automatically added STAR_EXCL port groups by calling br_multicast_del_pg(). For S,G entries, that deletion calls back into br_multicast_sg_del_exclude_ports(), so a large number of STAR_EXCL ports consumes one kernel stack frame per port and can hit the stack guard page.

Keep the complete port-group deletion path for cleanup, but suppress the S,G exclude-port cleanup while that helper is already walking the same entry. Normal deletion callers retain the existing behavior.

Affected

• Linux >= 8266a0491e92d39dc9af739e8380a0daa9b8836b < 695a5a4c69c922d9296b2d7ad5f1ce8c6858fc64
• Linux >= 8266a0491e92d39dc9af739e8380a0daa9b8836b < 2fb87c6025f90191516bee3ce14b42eb3e1cfed7
• Linux >= 8266a0491e92d39dc9af739e8380a0daa9b8836b < d109141ba14652146089ef78b32d5e4d5285ebad
• Linux >= 8266a0491e92d39dc9af739e8380a0daa9b8836b < 7931fb9181421953f3133b408b0f2e2b8dd68b61
• Linux >= 8266a0491e92d39dc9af739e8380a0daa9b8836b < 5158353121bae4f552cb677ce8c5c3ef52f93a0d
• Linux 5.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.