CVE-2026-23107

Description

In the Linux kernel, the following vulnerability has been resolved:arm64/fpsimd: signal: Allocate SSVE storage when restoring ZAThe code to restore a ZA context doesnt attempt to allocate the taskssve_state before setting TIF_SME. Consequently, restoring a ZA contextcan place a task into an invalid state where TIF_SME is set but thetasks sve_state is null.In legitimate but uncommon cases where the ZA signal context was NOTcreated by the kernel in the context of the same task (e.g. if the taskis saved/restored with something like CRIU), we have no guarantee thatsve_state had been allocated previously. In these cases, userspace canenter streaming mode without trapping while sve_state is null, causing alater null pointer dereference when the kernel attempts to store theregister state:| # ./sigreturn-za| Unable to handle kernel null pointer dereference at virtual address 0000000000000000| Mem abort info:| ESR = 0x0000000096000046| EC = 0x25: DABT (current EL), IL = 32 bits| SET = 0, FnV = 0| EA = 0, S1PTW = 0| FSC = 0x06: level 2 translation fault| Data abort info:| ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000| CM = 0, WnR = 1, TnD = 0, TagAccess = 0| GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0| user pgtable: 4k pages, 52-bit VAs, pgdp=0000000101f47c00| [0000000000000000] pgd=08000001021d8403, p4d=0800000102274403, pud=0800000102275403, pmd=0000000000000000| Internal error: Oops: 0000000096000046 [#1] SMP| Modules linked in:| CPU: 0 UID: 0 PID: 153 Comm: sigreturn-za Not tainted 6.19.0-rc1 #1 PREEMPT| Hardware name: linux,dummy-virt (DT)| pstate: 214000c9 (nzCv daIF +PAN -UAO -TCO +DIT -SSBS BTYPE=--)| pc : sve_save_state+0x4/0xf0| lr : fpsimd_save_user_state+0xb0/0x1c0| sp : ffff80008070bcc0| x29: ffff80008070bcc0 x28: fff00000c1ca4c40 x27: 63cfa172fb5cf658| x26: fff00000c1ca5228 x25: 0000000000000000 x24: 0000000000000000| x23: 0000000000000000 x22: fff00000c1ca4c40 x21: fff00000c1ca4c40| x20: 0000000000000020 x19: fff00000ff6900f0 x18: 0000000000000000| x17: fff05e8e0311f000 x16: 0000000000000000 x15: 028fca8f3bdaf21c| x14: 0000000000000212 x13: fff00000c0209f10 x12: 0000000000000020| x11: 0000000000200b20 x10: 0000000000000000 x9 : fff00000ff69dcc0| x8 : 00000000000003f2 x7 : 0000000000000001 x6 : fff00000c1ca5b48| x5 : fff05e8e0311f000 x4 : 0000000008000000 x3 : 0000000000000000| x2 : 0000000000000001 x1 : fff00000c1ca5970 x0 : 0000000000000440| Call trace:| sve_save_state+0x4/0xf0 (P)| fpsimd_thread_switch+0x48/0x198| __switch_to+0x20/0x1c0| __schedule+0x36c/0xce0| schedule+0x34/0x11c| exit_to_user_mode_loop+0x124/0x188| el0_interrupt+0xc8/0xd8| __el0_irq_handler_common+0x18/0x24| el0t_64_irq_handler+0x10/0x1c| el0t_64_irq+0x198/0x19c| Code: 54000040 d51b4408 d65f03c0 d503245f (e5bb5800)| ---[ end trace 0000000000000000 ]---Fix this by having restore_za_context() ensure that the tasks sve_stateis allocated, matching what we do when taking an SME trap. Any liveSVE/SSVE state (which is restored earlier from a separate signalcontext) must be preserved, and hence this is not zeroed.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234