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
