Patch "ARM: findbit: fix overflowing offset" has been added to the 4.19-stable tree

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This is a note to let you know that I've just added the patch titled

    ARM: findbit: fix overflowing offset

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-findbit-fix-overflowing-offset.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5710f0811478ec06dfd66cebaed5d3ef26952dec
Author: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Date:   Tue Jul 26 23:51:48 2022 +0100

    ARM: findbit: fix overflowing offset
    
    [ Upstream commit ec85bd369fd2bfaed6f45dd678706429d4f75b48 ]
    
    When offset is larger than the size of the bit array, we should not
    attempt to access the array as we can perform an access beyond the
    end of the array. Fix this by changing the pre-condition.
    
    Using "cmp r2, r1; bhs ..." covers us for the size == 0 case, since
    this will always take the branch when r1 is zero, irrespective of
    the value of r2. This means we can fix this bug without adding any
    additional code!
    
    Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
    Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S
index 7848780e8834..20fef6c41f6f 100644
--- a/arch/arm/lib/findbit.S
+++ b/arch/arm/lib/findbit.S
@@ -43,8 +43,8 @@ ENDPROC(_find_first_zero_bit_le)
  * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
  */
 ENTRY(_find_next_zero_bit_le)
-		teq	r1, #0
-		beq	3b
+		cmp	r2, r1
+		bhs	3b
 		ands	ip, r2, #7
 		beq	1b			@ If new byte, goto old routine
  ARM(		ldrb	r3, [r0, r2, lsr #3]	)
@@ -84,8 +84,8 @@ ENDPROC(_find_first_bit_le)
  * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
  */
 ENTRY(_find_next_bit_le)
-		teq	r1, #0
-		beq	3b
+		cmp	r2, r1
+		bhs	3b
 		ands	ip, r2, #7
 		beq	1b			@ If new byte, goto old routine
  ARM(		ldrb	r3, [r0, r2, lsr #3]	)
@@ -118,8 +118,8 @@ ENTRY(_find_first_zero_bit_be)
 ENDPROC(_find_first_zero_bit_be)
 
 ENTRY(_find_next_zero_bit_be)
-		teq	r1, #0
-		beq	3b
+		cmp	r2, r1
+		bhs	3b
 		ands	ip, r2, #7
 		beq	1b			@ If new byte, goto old routine
 		eor	r3, r2, #0x18		@ big endian byte ordering
@@ -152,8 +152,8 @@ ENTRY(_find_first_bit_be)
 ENDPROC(_find_first_bit_be)
 
 ENTRY(_find_next_bit_be)
-		teq	r1, #0
-		beq	3b
+		cmp	r2, r1
+		bhs	3b
 		ands	ip, r2, #7
 		beq	1b			@ If new byte, goto old routine
 		eor	r3, r2, #0x18		@ big endian byte ordering



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