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| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2024-09-26 01:25:38 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-10-22 16:51:34 +0300 |
| commit | 8a9e3d70bc97ac9bca7d28965ccff285085bf126 (patch) | |
| tree | 1af67cf6b8dbb1ba9f9fb84a038641e3ee515316 /arch | |
| parent | bbaa2bfa2f55014c257d436d2f576b51fec390d9 (diff) | |
| download | linux-8a9e3d70bc97ac9bca7d28965ccff285085bf126.tar.xz | |
x86/entry_32: Do not clobber user EFLAGS.ZF
commit 2e2e5143d4868163d6756c8c6a4d28cbfa5245e5 upstream.
Opportunistic SYSEXIT executes VERW to clear CPU buffers after user EFLAGS
are restored. This can clobber user EFLAGS.ZF.
Move CLEAR_CPU_BUFFERS before the user EFLAGS are restored. This ensures
that the user EFLAGS.ZF is not clobbered.
Closes: https://lore.kernel.org/lkml/yVXwe8gvgmPADpRB6lXlicS2fcHoV5OHHxyuFbB_MEleRPD7-KhGe5VtORejtPe-KCkT8Uhcg5d7-IBw4Ojb4H7z5LQxoZylSmJ8KNL3A8o=@protonmail.com/
Fixes: a0e2dab44d22 ("x86/entry_32: Add VERW just before userspace transition")
Reported-by: Jari Ruusu <jariruusu@protonmail.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240925-fix-dosemu-vm86-v7-1-1de0daca2d42%40linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/entry/entry_32.S | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index d3a814efbff6..9ad6cd89b7ac 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -871,6 +871,8 @@ SYM_FUNC_START(entry_SYSENTER_32) /* Now ready to switch the cr3 */ SWITCH_TO_USER_CR3 scratch_reg=%eax + /* Clobbers ZF */ + CLEAR_CPU_BUFFERS /* * Restore all flags except IF. (We restore IF separately because @@ -881,7 +883,6 @@ SYM_FUNC_START(entry_SYSENTER_32) BUG_IF_WRONG_CR3 no_user_check=1 popfl popl %eax - CLEAR_CPU_BUFFERS /* * Return back to the vDSO, which will pop ecx and edx. |