CVE-2026-98861
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() unregister_fprobe() and unregister_fprobe_async() (used by BPF kprobe-multi) rely on standard RCU grace periods (synchronize_rcu() and call_rcu()) to wait until in-flight fprobe handlers complete before freeing the fprobe. However, if an fprobe handler executes while RCU is not watching (such as in the idle loop or nohz_full extended quiescent states), standard RCU does not track preemption-disabled sections. Consequently, synchronize_rcu() does not wait for those executions, which can lead to a use-after-free if the fprobe is freed immediately after unregistration. Ensure handlers exit early when !rcu_is_watching(). Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep recursion if probed functions interact with lockdep. Since rhltable_lookup() and rhl_for_each_entry_rcu() use rcu_dereference_all_check() (which checks rcu_read_lock_any_held()), holding preemption disabled via rcu_read_lock_sched_notrace() is fully valid and sufficient so long as rcu_is_watching() is true. Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(), fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path rcu_read_lock() and lockdep overhead while guaranteeing safe grace period synchronization.
View original CVE JSON
{
"id": "CVE-2026-98861",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-18T16:17:40.573",
"lastModified": "2026-10-19T10:19:50.187",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()\n\nunregister_fprobe() and unregister_fprobe_async() (used by BPF\nkprobe-multi) rely on standard RCU grace periods (synchronize_rcu()\nand call_rcu()) to wait until in-flight fprobe handlers complete before\nfreeing the fprobe.\n\nHowever, if an fprobe handler executes while RCU is not watching (such\nas in the idle loop or nohz_full extended quiescent states), standard\nRCU does not track preemption-disabled sections. Consequently,\nsynchronize_rcu() does not wait for those executions, which can lead\nto a use-after-free if the fprobe is freed immediately after\nunregistration. Ensure handlers exit early when !rcu_is_watching().\n\nFurthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously\nused guard(rcu)() and rcu_read_lock(), which invoke lockdep on every\nhit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep\nrecursion if probed functions interact with lockdep.\n\nSince rhltable_lookup() and rhl_for_each_entry_rcu() use\nrcu_dereference_all_check() (which checks rcu_read_lock_any_held()),\nholding preemption disabled via rcu_read_lock_sched_notrace() is fully\nvalid and sufficient so long as rcu_is_watching() is true.\n\nDefine and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(),\nfprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path\nrcu_read_lock() and lockdep overhead while guaranteeing safe grace\nperiod synchronization."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"kernel/trace/fprobe.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "56b4cfcf1518245493c60fd39c56978f508f1816",
"lessThan": "a85d0f00671b4d4527317c10ba018680f7d8d673",
"versionType": "git",
"status": "affected"
},
{
"version": "657b594b2084b39a4bc6d8493aa2140cb00cea49",
"lessThan": "dd4a0d4993633b45470abf6da4ea0ca563402245",
"versionType": "git",
"status": "affected"
},
{
"version": "657b594b2084b39a4bc6d8493aa2140cb00cea49",
"lessThan": "e0a6249190402a28f1e2925a81acf573157d55ef",
"versionType": "git",
"status": "affected"
},
{
"version": "a4f6a9005ed6cfd360ef2520430927f05f92ffb0",
"versionType": "git",
"status": "affected"
},
{
"version": "6.18.34",
"lessThan": "6.18.56",
"versionType": "semver",
"status": "affected"
},
{
"version": "7.0.11",
"lessThan": "7.1",
"versionType": "semver",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"kernel/trace/fprobe.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "7.1",
"status": "affected"
},
{
"version": "0",
"lessThan": "7.1",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.56",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.10",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/a85d0f00671b4d4527317c10ba018680f7d8d673",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/dd4a0d4993633b45470abf6da4ea0ca563402245",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/e0a6249190402a28f1e2925a81acf573157d55ef",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}