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| author | Jan Beulich <jbeulich@suse.com> | 2019-11-18 16:21:12 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-11-29 10:08:02 +0100 |
| commit | c449a9c1298dd212e5e1cede5dd48bb8ce2a0263 (patch) | |
| tree | 292086f8f3f1bae0e060b0f5fa1aaf13e5fb1e44 | |
| parent | 7609da8781ba261e66b8c6873b0c8a379ca3c5c4 (diff) | |
| download | linux-stable-c449a9c1298dd212e5e1cede5dd48bb8ce2a0263.tar.gz linux-stable-c449a9c1298dd212e5e1cede5dd48bb8ce2a0263.tar.bz2 linux-stable-c449a9c1298dd212e5e1cede5dd48bb8ce2a0263.zip | |
x86/stackframe/32: Repair 32-bit Xen PV
commit 81ff2c37f9e5d77593928df0536d86443195fd64 upstream.
Once again RPL checks have been introduced which don't account for a 32-bit
kernel living in ring 1 when running in a PV Xen domain. The case in
FIXUP_FRAME has been preventing boot.
Adjust BUG_IF_WRONG_CR3 as well to guard against future uses of the macro
on a code path reachable when running in PV mode under Xen; I have to admit
that I stopped at a certain point trying to figure out whether there are
present ones.
Fixes: 3c88c692c287 ("x86/stackframe/32: Provide consistent pt_regs")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Stable Team <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/0fad341f-b7f5-f859-d55d-f0084ee7087e@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/entry/entry_32.S | 4 | ||||
| -rw-r--r-- | arch/x86/include/asm/segment.h | 12 |
2 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 4f86928246e7..5e470eadc351 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -172,7 +172,7 @@ ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI .if \no_user_check == 0 /* coming from usermode? */ - testl $SEGMENT_RPL_MASK, PT_CS(%esp) + testl $USER_SEGMENT_RPL_MASK, PT_CS(%esp) jz .Lend_\@ .endif /* On user-cr3? */ @@ -217,7 +217,7 @@ testl $X86_EFLAGS_VM, 4*4(%esp) jnz .Lfrom_usermode_no_fixup_\@ #endif - testl $SEGMENT_RPL_MASK, 3*4(%esp) + testl $USER_SEGMENT_RPL_MASK, 3*4(%esp) jnz .Lfrom_usermode_no_fixup_\@ orl $CS_FROM_KERNEL, 3*4(%esp) diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index ac3892920419..6669164abadc 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -31,6 +31,18 @@ */ #define SEGMENT_RPL_MASK 0x3 +/* + * When running on Xen PV, the actual privilege level of the kernel is 1, + * not 0. Testing the Requested Privilege Level in a segment selector to + * determine whether the context is user mode or kernel mode with + * SEGMENT_RPL_MASK is wrong because the PV kernel's privilege level + * matches the 0x3 mask. + * + * Testing with USER_SEGMENT_RPL_MASK is valid for both native and Xen PV + * kernels because privilege level 2 is never used. + */ +#define USER_SEGMENT_RPL_MASK 0x2 + /* User mode is privilege level 3: */ #define USER_RPL 0x3 |