Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting for once, to make this easily accessible to everyone. Is there hope that patches like these makes it to mainline any time soon? I fully understand that this it a hard problem, but in the end what triggered this were at least two regression reports afaics: https://bugzilla.kernel.org/show_bug.cgi?id=218707 https://lore.kernel.org/lkml/IdYcxU6x6xuUqUg8cliJUnucfwfTO29TrKIlLGCCYbbIr1EQnP0ZAtTxdAM2hp5e5Gny_acIN3OFDS6v0sazocnZZ1UBaINEJ0HoDnbasSI=@protonmail.com/ Sure, the older one was in April, so one week more or less now won't make much of a difference. But I think it still would be great to get this fixed rather sooner than later. Or where those issues meanwhile fixed through other patches without me noticing and I'm making a fool of myself here? This yet again makes me wonder if some "[regression fix]" in the subject or "CC: regressions@xxxxxxxxxxxxxxx" in the patches would help to make the regression aspect obvious to everyone involved. But it would create yet another small bit of overhead... :-/ Pawan Gupta, btw: many thx for working on this and sticking to it! Ciao, Thorsten On 26.09.24 00:25, Pawan Gupta wrote: > Changes in v7: > - Using %ss for verw fails kselftest ldt_gdt.c in 32-bit mode, use safer %cs instead (Dave). > > v6: https://lore.kernel.org/r/20240905-fix-dosemu-vm86-v6-0-7aff8e53cbbf@xxxxxxxxxxxxxxx > - Use %ss in 64-bit mode as well for all VERW calls. This avoids any having > a separate macro for 32-bit (Dave). > - Split 32-bit mode fixes into separate patches. > > v5: https://lore.kernel.org/r/20240711-fix-dosemu-vm86-v5-1-e87dcd7368aa@xxxxxxxxxxxxxxx > - Simplify the use of ALTERNATIVE construct (Uros/Jiri/Peter). > > v4: https://lore.kernel.org/r/20240710-fix-dosemu-vm86-v4-1-aa6464e1de6f@xxxxxxxxxxxxxxx > - Further simplify the patch by using %ss for all VERW calls in 32-bit mode (Brian). > - In NMI exit path move VERW after RESTORE_ALL_NMI that touches GPRs (Dave). > > v3: https://lore.kernel.org/r/20240701-fix-dosemu-vm86-v3-1-b1969532c75a@xxxxxxxxxxxxxxx > - Simplify CLEAR_CPU_BUFFERS_SAFE by using %ss instead of %ds (Brian). > - Do verw before popf in SYSEXIT path (Jari). > > v2: https://lore.kernel.org/r/20240627-fix-dosemu-vm86-v2-1-d5579f698e77@xxxxxxxxxxxxxxx > - Safe guard against any other system calls like vm86() that might change %ds (Dave). > > v1: https://lore.kernel.org/r/20240426-fix-dosemu-vm86-v1-1-88c826a3f378@xxxxxxxxxxxxxxx > > Hi, > > This series fixes a #GP in 32-bit kernels when executing vm86() system call > in dosemu software. In 32-bit mode, their are cases when user can set an > arbitrary %ds that can cause a #GP when executing VERW instruction. The > fix is to use %ss for referencing the VERW operand. > > Patch 1-2: Fixes the VERW callsites in 32-bit entry path. > Patch 3: Uses %ss for VERW in 32-bit and 64-bit mode. > > The fix is tested with below kselftest on 32-bit kernel: > > ./tools/testing/selftests/x86/entry_from_vm86.c > > 64-bit kernel was boot tested. On a Rocket Lake, measuring the CPU cycles > for VERW with and without the %ss shows no significant difference. This > indicates that the scrubbing behavior of VERW is intact. > > Thanks, > Pawan > > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> > --- > Pawan Gupta (3): > x86/entry_32: Do not clobber user EFLAGS.ZF > x86/entry_32: Clear CPU buffers after register restore in NMI return > x86/bugs: Use code segment selector for VERW operand > > arch/x86/entry/entry_32.S | 6 ++++-- > arch/x86/include/asm/nospec-branch.h | 6 ++++-- > 2 files changed, 8 insertions(+), 4 deletions(-) > --- > base-commit: 431c1646e1f86b949fa3685efc50b660a364c2b6 > change-id: 20240426-fix-dosemu-vm86-dd111a01737e > > Best regards, #regzbot poke
