musl: Fix CVE-2019-14697

musl libc through 1.1.23 has an x87 floating-point stack adjustment
imbalance, related to the math/i386/ directory. In some cases, use of
this library could introduce out-of-bounds writes that are not present
in an application's source code.

This problem only affects x86 and no other architectures.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
This commit is contained in:
Hauke Mehrtens 2019-08-18 23:24:43 +02:00
parent 9cdb4753be
commit c262daf308
3 changed files with 208 additions and 1 deletions

View File

@ -9,7 +9,7 @@ include $(INCLUDE_DIR)/target.mk
PKG_NAME:=musl
PKG_VERSION:=1.1.23
PKG_RELEASE:=2
PKG_RELEASE:=3
PKG_SOURCE_PROTO:=git
PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)

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@ -0,0 +1,179 @@
From f3ed8bfe8a82af1870ddc8696ed4cc1d5aa6b441 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Mon, 5 Aug 2019 18:41:47 -0400
Subject: fix x87 stack imbalance in corner cases of i386 math asm
commit 31c5fb80b9eae86f801be4f46025bc6532a554c5 introduced underflow
code paths for the i386 math asm, along with checks on the fpu status
word to skip the underflow-generation instructions if the underflow
flag was already raised. unfortunately, at least one such path, in
log1p, returned with 2 items on the x87 stack rather than just 1 item
for the return value. this is a violation of the ABI's calling
convention, and could cause subsequent floating point code to produce
NANs due to x87 stack overflow. if floating point results are used in
flow control, this can lead to runaway wrong code execution.
rather than reviewing each "underflow already raised" code path for
correctness, remove them all. they're likely slower than just
performing the underflow code unconditionally, and significantly more
complex.
all of this code should be ripped out and replaced by C source files
with inline asm. doing so would preclude this kind of error by having
the compiler perform all x87 stack register allocation and stack
manipulation, and would produce comparable or better code. however
such a change is a much larger project.
---
src/math/i386/asin.s | 10 ++--------
src/math/i386/atan.s | 7 ++-----
src/math/i386/atan2.s | 5 +----
src/math/i386/atan2f.s | 5 +----
src/math/i386/atanf.s | 7 ++-----
src/math/i386/exp.s | 10 ++--------
src/math/i386/log1p.s | 7 ++-----
src/math/i386/log1pf.s | 7 ++-----
8 files changed, 14 insertions(+), 44 deletions(-)
--- a/src/math/i386/asin.s
+++ b/src/math/i386/asin.s
@@ -7,13 +7,10 @@ asinf:
cmp $0x01000000,%eax
jae 1f
# subnormal x, return x with underflow
- fnstsw %ax
- and $16,%ax
- jnz 2f
fld %st(0)
fmul %st(1)
fstps 4(%esp)
-2: ret
+ ret
.global asinl
.type asinl,@function
@@ -30,11 +27,8 @@ asin:
cmp $0x00200000,%eax
jae 1f
# subnormal x, return x with underflow
- fnstsw %ax
- and $16,%ax
- jnz 2f
fsts 4(%esp)
-2: ret
+ ret
1: fld %st(0)
fld1
fsub %st(0),%st(1)
--- a/src/math/i386/atan.s
+++ b/src/math/i386/atan.s
@@ -10,8 +10,5 @@ atan:
fpatan
ret
# subnormal x, return x with underflow
-1: fnstsw %ax
- and $16,%ax
- jnz 2f
- fsts 4(%esp)
-2: ret
+1: fsts 4(%esp)
+ ret
--- a/src/math/i386/atan2.s
+++ b/src/math/i386/atan2.s
@@ -10,8 +10,5 @@ atan2:
cmp $0x00200000,%eax
jae 1f
# subnormal x, return x with underflow
- fnstsw %ax
- and $16,%ax
- jnz 1f
fsts 4(%esp)
-1: ret
+ ret
--- a/src/math/i386/atan2f.s
+++ b/src/math/i386/atan2f.s
@@ -10,10 +10,7 @@ atan2f:
cmp $0x01000000,%eax
jae 1f
# subnormal x, return x with underflow
- fnstsw %ax
- and $16,%ax
- jnz 1f
fld %st(0)
fmul %st(1)
fstps 4(%esp)
-1: ret
+ ret
--- a/src/math/i386/atanf.s
+++ b/src/math/i386/atanf.s
@@ -10,10 +10,7 @@ atanf:
fpatan
ret
# subnormal x, return x with underflow
-1: fnstsw %ax
- and $16,%ax
- jnz 2f
- fld %st(0)
+1: fld %st(0)
fmul %st(1)
fstps 4(%esp)
-2: ret
+ ret
--- a/src/math/i386/exp.s
+++ b/src/math/i386/exp.s
@@ -7,13 +7,10 @@ expm1f:
cmp $0x01000000,%eax
jae 1f
# subnormal x, return x with underflow
- fnstsw %ax
- and $16,%ax
- jnz 2f
fld %st(0)
fmul %st(1)
fstps 4(%esp)
-2: ret
+ ret
.global expm1l
.type expm1l,@function
@@ -30,11 +27,8 @@ expm1:
cmp $0x00200000,%eax
jae 1f
# subnormal x, return x with underflow
- fnstsw %ax
- and $16,%ax
- jnz 2f
fsts 4(%esp)
-2: ret
+ ret
1: fldl2e
fmulp
mov $0xc2820000,%eax
--- a/src/math/i386/log1p.s
+++ b/src/math/i386/log1p.s
@@ -16,9 +16,6 @@ log1p:
fyl2x
ret
# subnormal x, return x with underflow
-2: fnstsw %ax
- and $16,%ax
- jnz 1f
- fsts 4(%esp)
+2: fsts 4(%esp)
fstp %st(1)
-1: ret
+ ret
--- a/src/math/i386/log1pf.s
+++ b/src/math/i386/log1pf.s
@@ -16,10 +16,7 @@ log1pf:
fyl2x
ret
# subnormal x, return x with underflow
-2: fnstsw %ax
- and $16,%ax
- jnz 1f
- fxch
+2: fxch
fmul %st(1)
fstps 4(%esp)
-1: ret
+ ret

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@ -0,0 +1,28 @@
From 6818c31c9bc4bbad5357f1de14bedf781e5b349e Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Mon, 5 Aug 2019 19:57:07 -0400
Subject: fix build regression in i386 asm for atan2, atan2f
commit f3ed8bfe8a82af1870ddc8696ed4cc1d5aa6b441 inadvertently removed
labels that were still needed.
---
src/math/i386/atan2.s | 2 +-
src/math/i386/atan2f.s | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
--- a/src/math/i386/atan2.s
+++ b/src/math/i386/atan2.s
@@ -11,4 +11,4 @@ atan2:
jae 1f
# subnormal x, return x with underflow
fsts 4(%esp)
- ret
+1: ret
--- a/src/math/i386/atan2f.s
+++ b/src/math/i386/atan2f.s
@@ -13,4 +13,4 @@ atan2f:
fld %st(0)
fmul %st(1)
fstps 4(%esp)
- ret
+1: ret