| Message ID | dbe69b13f77052abf5d342b2775b1ebdbcce241a.1567077734.git.viresh.kumar@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | V4.4 backport of arm64 Spectre patches | expand |
On Thu, Aug 29, 2019 at 05:03:52PM +0530, Viresh Kumar wrote: > From: Will Deacon <will.deacon@arm.com> > > commit c2f0ad4fc089cff81cef6a13d04b399980ecbfcc upstream. > > A mispredicted conditional call to set_fs could result in the wrong > addr_limit being forwarded under speculation to a subsequent access_ok > check, potentially forming part of a spectre-v1 attack using uaccess > routines. > > This patch prevents this forwarding from taking place, but putting heavy > barriers in set_fs after writing the addr_limit. > > Reviewed-by: Mark Rutland <mark.rutland@arm.com> > Signed-off-by: Will Deacon <will.deacon@arm.com> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> [v4.4 backport] Mark. > --- > arch/arm64/include/asm/uaccess.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > index 75363d723262..fc11c50af558 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -62,6 +62,13 @@ extern int fixup_exception(struct pt_regs *regs); > static inline void set_fs(mm_segment_t fs) > { > current_thread_info()->addr_limit = fs; > + > + /* > + * Prevent a mispredicted conditional call to set_fs from forwarding > + * the wrong address limit to access_ok under speculation. > + */ > + dsb(nsh); > + isb(); > } > > #define segment_eq(a, b) ((a) == (b)) > -- > 2.21.0.rc0.269.g1a574e7a288b >
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 75363d723262..fc11c50af558 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -62,6 +62,13 @@ extern int fixup_exception(struct pt_regs *regs); static inline void set_fs(mm_segment_t fs) { current_thread_info()->addr_limit = fs; + + /* + * Prevent a mispredicted conditional call to set_fs from forwarding + * the wrong address limit to access_ok under speculation. + */ + dsb(nsh); + isb(); } #define segment_eq(a, b) ((a) == (b))