diff mbox series

[v3] arm: memcpy: fix copying big data does not meet expectations [BZ #25620]

Message ID ac494a6febda4430857df1fc31f64e19@huawei.com
State New
Headers show
Series [v3] arm: memcpy: fix copying big data does not meet expectations [BZ #25620] | expand

Commit Message

zhuyan (M) May 12, 2020, 12:01 p.m. UTC
In ARMv7, the memcpy() implementation allows for program execution to continue in scenarios where a segmentation fault or crash should have occurred. The dangers occur in that subsequent execution and iterations of this code will be executed with this corrupted data.

Such as, we use 'memcpy' copy 0x80000000 byte to buffer(The buffer size is 100 bytes), it didn't crash.

The essence of the problem is that the memcpy implementation uses signed instructions. So, we use unsigned instructions instead of signed instructions.

Signed-off-by: Yan Zhu <zhuyan34@huawei.com>
---
 sysdeps/arm/armv7/multiarch/memcpy_impl.S | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Comments

Florian Weimer May 13, 2020, 12:36 p.m. UTC | #1
* zhuyan:

> In ARMv7, the memcpy() implementation allows for program execution
> to continue in scenarios where a segmentation fault or crash should
> have occurred. The dangers occur in that subsequent execution and
> iterations of this code will be executed with this corrupted data.
>
> Such as, we use 'memcpy' copy 0x80000000 byte to buffer(The buffer
> size is 100 bytes), it didn't crash.
>
> The essence of the problem is that the memcpy implementation uses
> signed instructions. So, we use unsigned instructions instead of
> signed instructions.

Sorry, this still does not fix the new string/tst-memmove-overflow
overflow test I added recently:

info: testing memmove
tst-memmove-overflow.c:136: error: blob comparison failed
  blob length: 128 bytes
  left (evaluated from expected_start):
      "O\036m<\vZ)xG\027f5\004S\"q@\017_.}L\033j9\bW\'vE\024c2\001P\037o>\r\\+zI\030g6\006U$sB\021`/~N\035l;\nY(wF\026e4\003R!p?\016^-|K\032i8\aV%uD\023b1\000O\036m=\f[*yH\027f5\005T#rA\020_.}M\034k:\tX\'vE\025d3\002Q o>\r"
      4F 1E 6D 3C 0B 5A 29 78 47 17 66 35 04 53 22 71 40 0F 5F 2E 7D 4C 1B 6A 39 08 57 27 76 45 14 63 32 01 50 1F 6F 3E 0D 5C 2B 7A 49 18 67 36 06 55 24 73 42 11 60 2F 7E 4E 1D 6C 3B 0A 59 28 77 46 16 65 34 03 52 21 70 3F 0E 5E 2D 7C 4B 1A 69 38 07 56 25 75 44 13 62 31 00 4F 1E 6D 3D 0C 5B 2A 79 48 17 66 35 05 54 23 72 41 10 5F 2E 7D 4D 1C 6B 3A 09 58 27 76 45 15 64 33 02 51 20 6F 3E 0D
  right (evaluated from start):
      "O\036mm<\vZ)xG\027f5\004S\"q@\017_.}L\033j9\bW\'vE\024c2\001P\037o>\r\\+zI\030g6\006U$sB\021`/~N\035l;\nY(wF\026e4\003R!p?\016^-|K\032i8\aV%uD\023b1\000O\036m=\f[*yH\027f5\005T#rA\020_.}M\034k:\tX\'vE\025d3\002Q o>"
      4F 1E 6D 6D 3C 0B 5A 29 78 47 17 66 35 04 53 22 71 40 0F 5F 2E 7D 4C 1B 6A 39 08 57 27 76 45 14 63 32 01 50 1F 6F 3E 0D 5C 2B 7A 49 18 67 36 06 55 24 73 42 11 60 2F 7E 4E 1D 6C 3B 0A 59 28 77 46 16 65 34 03 52 21 70 3F 0E 5E 2D 7C 4B 1A 69 38 07 56 25 75 44 13 62 31 00 4F 1E 6D 3D 0C 5B 2A 79 48 17 66 35 05 54 23 72 41 10 5F 2E 7D 4D 1C 6B 3A 09 58 27 76 45 15 64 33 02 51 20 6F 3E
tst-memmove-overflow.c:139: error: blob comparison failed
  blob length: 128 bytes
  left (evaluated from expected_end):
      " o>\r\\+{J\031h7\006U$sC\022a0\177N\035l;\nZ)xG\026e4\003R\"q@\017^-|K\032j9\bW&uD\023b2\001P\037n=\f[*yI\030g6\005T#rA\021`/~M\034k:\tY(wF\025d3\002Q!p?\016],{J\031h8\aV%tC\022a0\000O\036m<\vZ)xH\027f5\004S\"q@\020_"
      20 6F 3E 0D 5C 2B 7B 4A 19 68 37 06 55 24 73 43 12 61 30 7F 4E 1D 6C 3B 0A 5A 29 78 47 16 65 34 03 52 22 71 40 0F 5E 2D 7C 4B 1A 6A 39 08 57 26 75 44 13 62 32 01 50 1F 6E 3D 0C 5B 2A 79 49 18 67 36 05 54 23 72 41 11 60 2F 7E 4D 1C 6B 3A 09 59 28 77 46 15 64 33 02 51 21 70 3F 0E 5D 2C 7B 4A 19 68 38 07 56 25 74 43 12 61 30 00 4F 1E 6D 3C 0B 5A 29 78 48 17 66 35 04 53 22 71 40 10 5F
  right (evaluated from start + allocation_size - sizeof (expected_end) - 1):
      "Q o>\r\\+{J\031h7\006U$sC\022a0\177N\035l;\nZ)xG\026e4\003R\"q@\017^-|K\032j9\bW&uD\023b2\001P\037n=\f[*yI\030g6\005T#rA\021`/~M\034k:\tY(wF\025d3\002Q!p?\016],{J\031h8\aV%tC\022a0\000O\036m<\vZ)xH\027f5\004S\"q@\020"
      51 20 6F 3E 0D 5C 2B 7B 4A 19 68 37 06 55 24 73 43 12 61 30 7F 4E 1D 6C 3B 0A 5A 29 78 47 16 65 34 03 52 22 71 40 0F 5E 2D 7C 4B 1A 6A 39 08 57 26 75 44 13 62 32 01 50 1F 6E 3D 0C 5B 2A 79 49 18 67 36 05 54 23 72 41 11 60 2F 7E 4D 1C 6B 3A 09 59 28 77 46 15 64 33 02 51 21 70 3F 0E 5D 2C 7B 4A 19 68 38 07 56 25 74 43 12 61 30 00 4F 1E 6D 3C 0B 5A 29 78 48 17 66 35 04 53 22 71 40 10

The difference between the two byte patterns is:

4F 1E 6D {+6D+} 3C 0B 5A 29 78 47 17 66 35 04 53 22 71 40 0F 5F 2E 7D 4C 1B 6A 39 08 57 27 76 45 14 63 32 01 50 1F 6F 3E 0D 5C 2B 7A 49 18 67 36 06 55 24 73 42 11 60 2F 7E 4E 1D 6C 3B 0A 59 28 77 46 16 65 34 03 52 21 70 3F 0E 5E 2D 7C 4B 1A 69 38 07 56 25 75 44 13 62 31 00 4F 1E 6D 3D 0C 5B 2A 79 48 17 66 35 05 54 23 72 41 10 5F 2E 7D 4D 1C 6B 3A 09 58 27 76 45 15 64 33 02 51 20 6F 3E [-0D-]

So it looks like it stopped copying after the first three bytes
because the shift stopped there.

I'm going to XFAIL the new test on arm, as requested by Andreas.
diff mbox series

Patch

diff --git a/sysdeps/arm/armv7/multiarch/memcpy_impl.S b/sysdeps/arm/armv7/multiarch/memcpy_impl.S
index bf4ac7077f..068474f0ea 100644
--- a/sysdeps/arm/armv7/multiarch/memcpy_impl.S
+++ b/sysdeps/arm/armv7/multiarch/memcpy_impl.S
@@ -268,7 +268,7 @@  ENTRY(memcpy)
 
 	mov	dst, dstin	/* Preserve dstin, we need to return it.  */
 	cmp	count, #64
-	bge	.Lcpy_not_short
+	bhs	.Lcpy_not_short
 	/* Deal with small copies quickly by dropping straight into the
 	   exit block.  */
 
@@ -351,10 +351,10 @@  ENTRY(memcpy)
 
 1:
 	subs	tmp2, count, #64	/* Use tmp2 for count.  */
-	blt	.Ltail63aligned
+	blo	.Ltail63aligned
 
 	cmp	tmp2, #512
-	bge	.Lcpy_body_long
+	bhs	.Lcpy_body_long
 
 .Lcpy_body_medium:			/* Count in tmp2.  */
 #ifdef USE_VFP
@@ -378,7 +378,7 @@  ENTRY(memcpy)
 	add	src, src, #64
 	vstr	d1, [dst, #56]
 	add	dst, dst, #64
-	bge	1b
+	bhs	1b
 	tst	tmp2, #0x3f
 	beq	.Ldone
 
@@ -412,7 +412,7 @@  ENTRY(memcpy)
 	ldrd	A_l, A_h, [src, #64]!
 	strd	A_l, A_h, [dst, #64]!
 	subs	tmp2, tmp2, #64
-	bge	1b
+	bhs	1b
 	tst	tmp2, #0x3f
 	bne	1f
 	ldr	tmp2,[sp], #FRAME_SIZE
@@ -482,7 +482,7 @@  ENTRY(memcpy)
 	add	src, src, #32
 
 	subs	tmp2, tmp2, #prefetch_lines * 64 * 2
-	blt	2f
+	blo	2f
 1:
 	cpy_line_vfp	d3, 0
 	cpy_line_vfp	d4, 64
@@ -494,7 +494,7 @@  ENTRY(memcpy)
 	add	dst, dst, #2 * 64
 	add	src, src, #2 * 64
 	subs	tmp2, tmp2, #prefetch_lines * 64
-	bge	1b
+	bhs	1b
 
 2:
 	cpy_tail_vfp	d3, 0