bridge: Fix sleep in atomic context in sysfs path

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63988
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:18 UTC
Updated2026-07-19 16:17:18 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bridge: Fix sleep in atomic context in sysfs path Since the start of the git history, brport_store() always acquired the bridge lock. Back then this decision made sense: The bridge lock protects the STP state of the bridge and its ports and at that time the function was only used by two STP related attributes (cost and priority). Nowadays, brport_store() processes a lot more attributes and most of them do not need the bridge lock: * Bridge flags: Only require RTNL. Read locklessly by the data path. Annotations can be added in net-next. * FDB port flushing: Only requires the FDB lock. * Multicast attributes: Only require the multicast lock. * Group forward mask: Only requires RTNL. Read locklessly by the data path. Annotations can be added in net-next. * Backup port: Only requires RTNL. Read locklessly by the data path. This is a problem as the bridge calls dev_set_promiscuity() when certain bridge port flags change and this function can sleep since the commit cited below, resulting in a splat such as [1]. Fix this by reducing the scope of the bridge lock and only take it when processing the two STP related attributes that require it. Remove the now stale comment from br_switchdev_set_port_flag(). The SWITCHDEV_F_DEFER flag can be removed in net-next. [1] BUG: sleeping function called from invalid context at net/core/dev_addr_lists.c:1262 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 372, name: bash preempt_count: 201, expected: 0 RCU nest depth: 0, expected: 0 5 locks held by bash/372: #0: ffff88810c51c3f0 (sb_writers#7){.+.+}-{0:0}, at: ksys_write (fs/read_write.c:740) #1: ffff888115ce9480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter (fs/kernfs/file.c:343) #2: ffff88810b9fd330 (kn->active#37){.+.+}-{0:0}, at: kernfs_fop_write_iter (fs/kernfs/file.c:80 fs/kernfs/file.c:344) #3: ffffffffa59473a0 (rtnl_mutex){+.+.}-{4:4}, at: brport_store (net/bridge/br_sysfs_if.c:326) #4: ffff8881099d2d58 (&br->lock){+...}-{3:3}, at: brport_store (./include/linux/spinlock.h:348 net/bridge/br_sysfs_if.c:345) Preemption disabled at: 0x0 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120) __might_resched.cold (kernel/sched/core.c:9163) netif_rx_mode_run (net/core/dev_addr_lists.c:1262) netif_rx_mode_sync (net/core/dev_addr_lists.c:1428) dev_set_promiscuity (net/core/dev_api.c:289) br_manage_promisc (net/bridge/br_if.c:135 net/bridge/br_if.c:172) br_port_flags_change (net/bridge/br_if.c:242 net/bridge/br_if.c:747) store_learning (net/bridge/br_sysfs_if.c:79 net/bridge/br_sysfs_if.c:235) brport_store (net/bridge/br_sysfs_if.c:346) kernfs_fop_write_iter (fs/kernfs/file.c:352) new_sync_write (fs/read_write.c:595) vfs_write (fs/read_write.c:688) ksys_write (fs/read_write.c:740) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

Risk And Classification

EPSS: 0.001660000 probability, percentile 0.061680000 (date 2026-07-20)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 78cd408356fe3edbac66598772fd347bf3e32c1f e976e3f2f2005c6267089a1a3b6344f234a59a55 git Not specified
CNA Linux Linux affected 78cd408356fe3edbac66598772fd347bf3e32c1f 2f9cb30d97e45686f3119fff3b30f12259950910 git Not specified
CNA Linux Linux affected 78cd408356fe3edbac66598772fd347bf3e32c1f 6d34594cc619d0d4b07d5afcad8b5984f3526dcf git Not specified
CNA Linux Linux affected 6.15 Not specified
CNA Linux Linux unaffected 6.15 semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/e976e3f2f2005c6267089a1a3b6344f234a59a55 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6d34594cc619d0d4b07d5afcad8b5984f3526dcf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2f9cb30d97e45686f3119fff3b30f12259950910 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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