CVE-2026-43249

9p/xen: protect xen_9pfs_front_free against concurrent calls

State: Published
Severity: 8.8 High
Published: May 6, 2026
Updated: Oct 30, 2026
Reserved: May 1, 2026

Description

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

9p/xen: protect xen_9pfs_front_free against concurrent calls

The xenwatch thread can race with other back-end change notifications and call xen_9pfs_front_free() twice, hitting the observed general protection fault due to a double-free. Guard the teardown path so only one caller can release the front-end state at a time, preventing the crash.

This is a fix for the following double-free:

[ 27.052347] Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI [ 27.052357] CPU: 0 UID: 0 PID: 32 Comm: xenwatch Not tainted 6.18.0-02087-g51ab33fc0a8b-dirty #60 PREEMPT(none) [ 27.052363] RIP: e030:xen_9pfs_front_free+0x1d/0x150 [ 27.052368] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 fd 48 c7 c7 48 d0 92 85 53 e8 cb cb 05 00 48 8b 45 08 48 8b 55 00 <48> 3b 28 0f 85 f9 28 35 fe 48 3b 6a 08 0f 85 ef 28 35 fe 48 89 42 [ 27.052377] RSP: e02b:ffffc9004016fdd0 EFLAGS: 00010246 [ 27.052381] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88800d66e400 RCX: 0000000000000000 [ 27.052385] RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000000 RDI: 0000000000000000 [ 27.052389] RBP: ffff88800a887040 R08: 0000000000000000 R09: 0000000000000000 [ 27.052393] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888009e46b68 [ 27.052397] R13: 0000000000000200 R14: 0000000000000000 R15: ffff88800a887040 [ 27.052404] FS: 0000000000000000(0000) GS:ffff88808ca57000(0000) knlGS:0000000000000000 [ 27.052408] CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.052412] CR2: 00007f9714004360 CR3: 0000000004834000 CR4: 0000000000050660 [ 27.052418] Call Trace: [ 27.052420] <TASK> [ 27.052422] xen_9pfs_front_changed+0x5d5/0x720 [ 27.052426] ? xenbus_otherend_changed+0x72/0x140 [ 27.052430] ? __pfx_xenwatch_thread+0x10/0x10 [ 27.052434] xenwatch_thread+0x94/0x1c0 [ 27.052438] ? __pfx_autoremove_wake_function+0x10/0x10 [ 27.052442] kthread+0xf8/0x240 [ 27.052445] ? __pfx_kthread+0x10/0x10 [ 27.052449] ? __pfx_kthread+0x10/0x10 [ 27.052452] ret_from_fork+0x16b/0x1a0 [ 27.052456] ? __pfx_kthread+0x10/0x10 [ 27.052459] ret_from_fork_asm+0x1a/0x30 [ 27.052463] </TASK> [ 27.052465] Modules linked in: [ 27.052471] ---[ end trace 0000000000000000 ]---

Scores

CVSS	Score	Vector	Source
3.1	8.8 High	CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	4f0e9244770f5b75a16d8c0929063cd336926764 to before 056709e2c6f121548df108a9fef2d1430b233e56Affected c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before 480aa6ffd4ac7036eea042047d0cca71bc2074bbAffected c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before a5d00dff97118a32fcf5fec7a4c3f864c4620c4eAffected c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before 59e7707492576bdbfa8c1dbe7d90791df31e4773Affected c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before bf841d43f7a33d75675ba7f4e214ac1c67913065Affected c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before ce8ded2e61f47747e31eeefb44dc24a2160a7e32Affected be03c4fe72384366fd4077a70966bd3b8fc49013Affected 1ab4de11232e83b875b071aa44d1155634ca8a1eAffected 7cc9dbae8a5f73bd555130384ea256018d28f283Affected 3e0359f151ac151abe3fa71040e450ed69cb824bAffected 8d3fc907d060c4fb33203e616a395a22083b6566Affected 5f6a8974e9ef317fe63f88bab1f33070195dd147Affected 6.1.18 to before 6.1.191Affected 4.14.308 to before 4.15Affected 4.19.276 to before 4.20Affected 5.4.235 to before 5.5Affected 5.10.173 to before 5.11Affected 5.15.100 to before 5.16Affected 6.2.5 to before 6.3Affected
LinuxLinux	6.3Affected before 6.3Not affected 6.1.191 through 6.1.Not affected 6.6.160 through 6.6.Not affected 6.12.75 through 6.12.Not affected 6.18.16 through 6.18.Not affected 6.19.6 through 6.19.*Not affected 7.0 and laterNot affected

Product

Versions

LinuxLinux

4f0e9244770f5b75a16d8c0929063cd336926764 to before 056709e2c6f121548df108a9fef2d1430b233e56Affected
c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before 480aa6ffd4ac7036eea042047d0cca71bc2074bbAffected
c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before a5d00dff97118a32fcf5fec7a4c3f864c4620c4eAffected
c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before 59e7707492576bdbfa8c1dbe7d90791df31e4773Affected
c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before bf841d43f7a33d75675ba7f4e214ac1c67913065Affected
c15fe55d14b3b4ded5af2a3260877460a6ffb8ad to before ce8ded2e61f47747e31eeefb44dc24a2160a7e32Affected
be03c4fe72384366fd4077a70966bd3b8fc49013Affected
1ab4de11232e83b875b071aa44d1155634ca8a1eAffected
7cc9dbae8a5f73bd555130384ea256018d28f283Affected
3e0359f151ac151abe3fa71040e450ed69cb824bAffected
8d3fc907d060c4fb33203e616a395a22083b6566Affected
5f6a8974e9ef317fe63f88bab1f33070195dd147Affected
6.1.18 to before 6.1.191Affected
4.14.308 to before 4.15Affected
4.19.276 to before 4.20Affected
5.4.235 to before 5.5Affected
5.10.173 to before 5.11Affected
5.15.100 to before 5.16Affected
6.2.5 to before 6.3Affected

LinuxLinux

6.3Affected
before 6.3Not affected
6.1.191 through 6.1.*Not affected
6.6.160 through 6.6.*Not affected
6.12.75 through 6.12.*Not affected
6.18.16 through 6.18.*Not affected
6.19.6 through 6.19.*Not affected
7.0 and laterNot affected

References

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