In the Linux kernel, the following vulnerability has been resolved: btrfs: fix space cache corruption and potential double allocations When testing space_cache v2 on a large set of machines, we encountered a few symptoms: 1. "unable to add free space :-17" (EEXIST) errors. 2. Missing free space info items, sometimes caught with a "missing free space info for X" error. 3. Double-accounted space: ranges that were allocated in the extent tree and also marked as free in the free space tree, ranges that were marked as allocated twice in the extent tree, or ranges that were marked as free twice in the free space tree. If the latter made it onto disk, the next reboot would hit the BUG_ON() in add_new_free_space(). 4. On some hosts with no on-disk corruption or error messages, the in-memory space cache (dumped with drgn) disagreed with the free space tree. All of these symptoms have the same underlying cause: a race between caching the free space for a block group and returning free space to the in-memory space cache for pinned extents causes us to double-add a free range to the space cache. This race exists when free space is cached from the free space tree (space_cache=v2) or the extent tree (nospace_cache, or space_cache=v1 if the cache needs to be regenerated). struct btrfs_block_group::last_byte_to_unpin and struct btrfs_block_group::progress are supposed to protect against this race, but commit d0c2f4fa555e ("btrfs: make concurrent fsyncs wait less when waiting for a transaction commit") subtly broke this by allowing multiple transactions to be unpinning extents at the same time. Specifically, the race is as follows: 1. An extent is deleted from an uncached block group in transaction A. 2. btrfs_commit_transaction() is called for transaction A. 3. btrfs_run_delayed_refs() -> __btrfs_free_extent() runs the delayed ref for the deleted extent. 4. __btrfs_free_extent() -> do_free_extent_accounting() -> add_to_free_space_tree() adds the deleted extent back to the free space tree. 5. do_free_extent_accounting() -> btrfs_update_block_group() -> btrfs_cache_block_group() queues up the block group to get cached. block_group->progress is set to block_group->start. 6. btrfs_commit_transaction() for transaction A calls switch_commit_roots(). It sets block_group->last_byte_to_unpin to block_group->progress, which is block_group->start because the block group hasn't been cached yet. 7. The caching thread gets to our block group. Since the commit roots were already switched, load_free_space_tree() sees the deleted extent as free and adds it to the space cache. It finishes caching and sets block_group->progress to U64_MAX. 8. btrfs_commit_transaction() advances transaction A to TRANS_STATE_SUPER_COMMITTED. 9. fsync calls btrfs_commit_transaction() for transaction B. Since transaction A is already in TRANS_STATE_SUPER_COMMITTED and the commit is for fsync, it advances. 10. btrfs_commit_transaction() for transaction B calls switch_commit_roots(). This time, the block group has already been cached, so it sets block_group->last_byte_to_unpin to U64_MAX. 11. btrfs_commit_transaction() for transaction A calls btrfs_finish_extent_commit(), which calls unpin_extent_range() for the deleted extent. It sees last_byte_to_unpin set to U64_MAX (by transaction B!), so it adds the deleted extent to the space cache again! This explains all of our symptoms above: * If the sequence of events is exactly as described above, when the free space is re-added in step 11, it will fail with EEXIST. * If another thread reallocates the deleted extent in between steps 7 and 11, then step 11 will silently re-add that space to the space cache as free even though it is actually allocated. Then, if that space is allocated *again*, the free space tree will be corrupted (namely, the wrong item will be deleted). * If we don't catch this free space tree corr ---truncated---

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - In the Linux kernel, the following vulnerability has been resolved: btrfs: fix space cache corruption and     potential double allocations When testing space_cache v2 on a large set of machines, we encountered a few     symptoms: 1. unable to add free space :-17 (EEXIST) errors. 2. Missing free space info items, sometimes     caught with a missing free space info for X error. 3. Double-accounted space: ranges that were allocated     in the extent tree and also marked as free in the free space tree, ranges that were marked as allocated     twice in the extent tree, or ranges that were marked as free twice in the free space tree. If the latter     made it onto disk, the next reboot would hit the BUG_ON() in add_new_free_space(). 4. On some hosts with     no on-disk corruption or error messages, the in-memory space cache (dumped with drgn) disagreed with the     free space tree. All of these symptoms have the same underlying cause: a race between caching the free     space for a block group and returning free space to the in-memory space cache for pinned extents causes us     to double-add a free range to the space cache. This race exists when free space is cached from the free     space tree (space_cache=v2) or the extent tree (nospace_cache, or space_cache=v1 if the cache needs to be     regenerated). struct btrfs_block_group::last_byte_to_unpin and struct btrfs_block_group::progress are     supposed to protect against this race, but commit d0c2f4fa555e (btrfs: make concurrent fsyncs wait less     when waiting for a transaction commit) subtly broke this by allowing multiple transactions to be     unpinning extents at the same time. Specifically, the race is as follows: 1. An extent is deleted from an     uncached block group in transaction A. 2. btrfs_commit_transaction() is called for transaction A. 3.
    btrfs_run_delayed_refs() -> __btrfs_free_extent() runs the delayed ref for the deleted extent. 4.
    __btrfs_free_extent() -> do_free_extent_accounting() -> add_to_free_space_tree() adds the deleted extent     back to the free space tree. 5. do_free_extent_accounting() -> btrfs_update_block_group() ->     btrfs_cache_block_group() queues up the block group to get cached. block_group->progress is set to     block_group->start. 6. btrfs_commit_transaction() for transaction A calls switch_commit_roots(). It sets     block_group->last_byte_to_unpin to block_group->progress, which is block_group->start because the block     group hasn't been cached yet. 7. The caching thread gets to our block group. Since the commit roots were     already switched, load_free_space_tree() sees the deleted extent as free and adds it to the space cache.
    It finishes caching and sets block_group->progress to U64_MAX. 8. btrfs_commit_transaction() advances     transaction A to TRANS_STATE_SUPER_COMMITTED. 9. fsync calls btrfs_commit_transaction() for transaction B.
    Since transaction A is already in TRANS_STATE_SUPER_COMMITTED and the commit is for fsync, it advances.
    10. btrfs_commit_transaction() for transaction B calls switch_commit_roots(). This time, the block group     has already been cached, so it sets block_group->last_byte_to_unpin to U64_MAX. 11.
    btrfs_commit_transaction() for transaction A calls btrfs_finish_extent_commit(), which calls     unpin_extent_range() for the deleted extent. It sees last_byte_to_unpin set to U64_MAX (by transaction     B!), so it adds the deleted extent to the space cache again! This explains all of our symptoms above: * If     the sequence of events is exactly as described above, when the free space is re-added in step 11, it will     fail with EEXIST. * If another thread reallocates the deleted extent in between steps 7 and 11, then step     11 will silently re-add that space to the space cache as free even though it is actually allocated. Then,     if that space is allocated *again*, the free space tree will be corrupted (namely, the wrong item will be     deleted). * If we don't catch this free space tree corr ---truncated--- (CVE-2022-49999)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:02537-1 advisory.

    The SUSE Linux Enterprise 15 SP4 kernel was updated to receive various security bugfixes.


    The following security bugs were fixed:

    - CVE-2021-47557: net/sched: sch_ets: do not peek at classes beyond 'nbands' (bsc#1207361 bsc#1225468).
    - CVE-2021-47595: net/sched: sch_ets: do not remove idle classes from the round-robin list (bsc#1207361     bsc#1226552).
    - CVE-2023-52924: netfilter: nf_tables: do not skip expired elements during walk (bsc#1236821).
    - CVE-2023-52925: netfilter: nf_tables: do not fail inserts if duplicate has expired (bsc#1236822).
    - CVE-2024-26808: netfilter: nft_chain_filter: handle NETDEV_UNREGISTER for inet/ingress basechain     (bsc#1222634).
    - CVE-2024-26924: scsi: lpfc: Release hbalock before calling lpfc_worker_wake_up() (bsc#1225820).
    - CVE-2024-27397: kabi: place tstamp needed for nftables set in a hole (bsc#1224095).
    - CVE-2024-36978: net: sched: sch_multiq: fix possible OOB write in multiq_tune() (bsc#1226514).
    - CVE-2024-46800: sch/netem: fix use after free in netem_dequeue (bsc#1230827).
    - CVE-2024-53057: net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT (bsc#1233551).
    - CVE-2024-53125: bpf: sync_linked_regs() must preserve subreg_def (bsc#1234156).
    - CVE-2024-53141: netfilter: ipset: add missing range check in bitmap_ip_uadt (bsc#1234381).
    - CVE-2024-56770: sch/netem: fix use after free in netem_dequeue (bsc#1235637).
    - CVE-2024-57947: netfilter: nf_set_pipapo: fix initial map fill (bsc#1236333).
    - CVE-2025-21700: net: sched: Disallow replacing of child qdisc from one parent to another (bsc#1237159).
    - CVE-2025-21702: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 (bsc#1237312).
    - CVE-2025-21703: netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() (bsc#1237313).
    - CVE-2025-21756: vsock: Orphan socket after transport release (bsc#1238876).
    - CVE-2025-23141: KVM: x86: Acquire SRCU in KVM_GET_MP_STATE to protect guest memory accesses     (bsc#1242782).
    - CVE-2025-37752: net_sched: sch_sfq: move the limit validation (bsc#1242504).
    - CVE-2025-37797: net_sched: hfsc: Fix a UAF vulnerability in class handling (bsc#1242417).
    - CVE-2025-37823: net_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too (bsc#1242924).
    - CVE-2025-37890: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc     (bsc#1243330).
    - CVE-2025-37997: netfilter: ipset: fix region locking in hash types (bsc#1243832).
    - CVE-2025-38000: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() (bsc#1244277).
    - CVE-2025-38001: net_sched: hfsc: Address reentrant enqueue adding class to eltree twice (bsc#1244234).
    - CVE-2025-38014: dmaengine: idxd: Refactor remove call with idxd_cleanup() helper (bsc#1244732).
    - CVE-2025-38083: net_sched: prio: fix a race in prio_tune() (bsc#1245183).


Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:02264-1 advisory.

    The SUSE Linux Enterprise 15 SP5 kernel was updated to receive various security bugfixes.


    The following security bugs were fixed:

    - CVE-2021-47557: net/sched: sch_ets: do not peek at classes beyond 'nbands' (bsc#1207361 bsc#1225468).
    - CVE-2021-47595: net/sched: sch_ets: do not remove idle classes from the round-robin list (bsc#1207361     bsc#1226552).
    - CVE-2023-52924: netfilter: nf_tables: do not skip expired elements during walk (bsc#1236821).
    - CVE-2023-52925: netfilter: nf_tables: do not fail inserts if duplicate has expired (bsc#1236822).
    - CVE-2024-26808: netfilter: nft_chain_filter: handle NETDEV_UNREGISTER for inet/ingress basechain     (bsc#1222634).
    - CVE-2024-26924: scsi: lpfc: Release hbalock before calling lpfc_worker_wake_up() (bsc#1225820).
    - CVE-2024-27397: kabi: place tstamp needed for nftables set in a hole (bsc#1224095).
    - CVE-2024-36978: net: sched: sch_multiq: fix possible OOB write in multiq_tune() (bsc#1226514).
    - CVE-2024-46800: sch/netem: fix use after free in netem_dequeue (bsc#1230827).
    - CVE-2024-53125: bpf: sync_linked_regs() must preserve subreg_def (bsc#1234156).
    - CVE-2024-53141: netfilter: ipset: add missing range check in bitmap_ip_uadt (bsc#1234381).
    - CVE-2024-53197: ALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devices     (bsc#1235464).
    - CVE-2024-56770: sch/netem: fix use after free in netem_dequeue (bsc#1235637).
    - CVE-2025-21700: net: sched: Disallow replacing of child qdisc from one parent to another (bsc#1237159).
    - CVE-2025-21702: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 (bsc#1237312).
    - CVE-2025-21703: netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() (bsc#1237313).
    - CVE-2025-21756: vsock: Orphan socket after transport release (bsc#1238876).
    - CVE-2025-23141: KVM: x86: Acquire SRCU in KVM_GET_MP_STATE to protect guest memory accesses     (bsc#1242782).
    - CVE-2025-37752: net_sched: sch_sfq: move the limit validation (bsc#1242504).
    - CVE-2025-37823: net_sched: hfsc: Fix a potential UAF in hfsc_dequeue() too (bsc#1242924).
    - CVE-2025-37890: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc     (bsc#1243330).
    - CVE-2025-37997: netfilter: ipset: fix region locking in hash types (bsc#1243832).
    - CVE-2025-38000: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue() (bsc#1244277).
    - CVE-2025-38001: net_sched: hfsc: Address reentrant enqueue adding class to eltree twice (bsc#1244234).
    - CVE-2025-38014: dmaengine: idxd: Refactor remove call with idxd_cleanup() helper (bsc#1244732).
    - CVE-2025-38060: bpf: abort verification if env->cur_state->loop_entry != NULL (bsc#1245155).
    - CVE-2025-38083: net_sched: prio: fix a race in prio_tune() (bsc#1245183).


Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
246220	Linux Distros Unpatched Vulnerability : CVE-2022-49999	Nessus	Misc.	high
242951	SUSE SLES15: cluster-md-kmp-default / dlm-kmp-default / gfs2-kmp-default / etc (SUSE-SU-2025:02537-1)	Nessus	SuSE Local Security Checks	high
241963	SUSE SLES15: cluster-md-kmp-default / dlm-kmp-default / gfs2-kmp-default / etc (SUSE-SU-2025:02264-1)	Nessus	SuSE Local Security Checks	high
166118	Amazon Linux 2 : kernel, --advisory ALAS2KERNEL-5.15-2022-008 (ALASKERNEL-5.15-2022-008)	Nessus	Amazon Linux Local Security Checks	high

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