In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
arm64\/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems<\/p>\n
When system_supports_sme() is true but system_supports_sve() is false,
\nrestoring a specifically crafted SVE signal context can result in the
\ntask erroneously having non-streaming SVE state. Subsequent attempts to
\nmanipulate the task’s FPSIMD\/SVE\/SME state can result in a variety of
\nproblems, including fatal EL1 UNDEFs.<\/p>\n
In such configurations, the kernel always creates an SVE signal context
\nwhen delivering a signal, and this can only be in one of two states:<\/p>\n
(1) SVE_SIG_FLAG_SM is set, and an SVE payload is present containing
\n streaming mode SVE state. The recorded VL is the task’s live
\n streaming VL.<\/p>\n
(2) SVE_SIG_FLAG_SM is clear, and an SVE payload is not present. The
\n FPSIMD context contains the non-streaming mode FPSIMD state. The
\n recorded VL is 0.<\/p>\n
Currently restore_sve_fpsimd_context() correctly rejects cases where
\nSVE_SIG_FLAG_SM is set and an SVE payload is not present, but fails to
\nreject cases where SVE_SIG_FLAG_SM is clear and an SVE payload is
\npresent. Consequently, restore_sve_fpsimd_context() can place the task
\nin a state where it has non-streaming SVE state even when this is not
\nsupported by HW.<\/p>\n
For example, this can cause a later EL1 UNDEF when the kernel attempts to
\nrestore the task’s ZCR_EL1 value:<\/p>\n
| # .\/sme-sigcontext-to-sve
\n| Internal error: Oops – Undefined instruction: 0000000002000000 [#1] SMP
\n| Modules linked in:
\n| CPU: 0 UID: 0 PID: 131 Comm: sme-sigcontext- Not tainted 7.3.0-rc1 #1 PREEMPT
\n| Hardware name: linux,dummy-virt (DT)
\n| pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=–)
\n| pc : fpsimd_restore_current_state+0x258\/0x458
\n| lr : exit_to_user_mode_loop+0xb8\/0x188
\n| sp : ffff80008056be40
\n| x29: ffff80008056be40 x28: fff00000c1670000 x27: 0000000000000000
\n| x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
\n| x23: ffff80008056bec0 x22: 0000000000000008 x21: 0000000000000040
\n| x20: 0000000000000081 x19: 0000000008800010 x18: 0000000000000000
\n| x17: 0000fffffd412570 x16: 0000000000001000 x15: 0000fffffd4123b0
\n| x14: 0000fffffd412780 x13: 0000fffffd412be8 x12: 0000000047435300
\n| x11: 0000fffffd412570 x10: 0000000000000000 x9 : 0000000045585401
\n| x8 : fff00000c18a6c44 x7 : 0000000000000000 x6 : 0000000000000002
\n| x5 : 0000000000000002 x4 : ffff800080568000 x3 : 0000000000000001
\n| x2 : 0000000008800010 x1 : fff00000c1670000 x0 : 0000000008800000
\n| Call trace:
\n| fpsimd_restore_current_state+0x258\/0x458 (P)
\n| exit_to_user_mode_loop+0xb8\/0x188
\n| el0_svc+0x1cc\/0x1d0
\n| el0t_64_sync_handler+0xa0\/0xe4
\n| el0t_64_sync+0x198\/0x19c
\n| Code: d5384101 f9400020 53175c03 36b80de0 (d5381202)
\n| —[ end trace 0000000000000000 ]—
\n| Kernel panic – not syncing: Oops – Undefined instruction: Fatal exception in interrupt
\n| Kernel Offset: 0x291fb1000000 from 0xffff800080000000
\n| PHYS_OFFSET: 0x40000000
\n| CPU features: 0x0,00000000,0052802f,ffb88f43,3afcf73f
\n| Memory Limit: none<\/p>\n
Rework restore_sve_fpsimd_context() to reject cases where
\nSVE_SIG_FLAG_SM is clear and an SVE payload is not present. As
\nparse_user_sigframe() rejects SVE signal frames when neither SVE nor SME
\nare supported, it isn’t necessary for restore_sve_fpsimd_context() to
\nhandle the case where neither are supported.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
arm64\/fpsimd: signal: Forbid non-streaming SVE payload on SME-only systems<\/p>\n
When system_supports_sme() is true but system_supports_<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-41217","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/41217","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41217"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41217"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41217"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}