[PATCH v2] bitops: make the *_bit_le functions use unsigned long

[Benjamin Marzinski]

The *_bit_le functions use a signed integer for the bit number.
However, the *_bit functions can use an unsigned long. This causes
problems if there is a large bitmap and a bit number > 0x80000000 is
passed in. Since that is a negative int, it will get sign extended to a
long when getting passed to the *_bit function, turning it into a huge
bit number. This usually ends up with the memory address wrapping around
and the function accessing memory before the start of the bitmap.

Avoid this by making the *_bit_le functions take an unsigned long.

This can be triggered by faking an almost 4TB dm-mirror device, which
uses bitmaps to track the mirror regions:

$ dmsetup create bigzero --table '0 8589934590 zero'
$ dmsetup create mymirror --table '0 8589934590 mirror core 2 2 nosync 2 /dev/mapper/bigzero 0 /dev/mapper/bigzero 0'

This will access memory before the start of the sync_bits bitmap, and
likely hit the guard page of the previously allocated clean_bits bitmap,
causing a kernel panic with the old code.

I looked and didn't see any crazy code using the signed int to
intentionally try and access bits before some address within the bitmap.

Signed-off-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
---

Changes from v1 (commit message only. No code changed):
- changed the commit message to correctly say that the functions now
  take unsigned long arguments from the bit nr
- Added the reproducer instructions to the commit message.

 include/asm-generic/bitops/le.h | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/asm-generic/bitops/le.h b/include/asm-generic/bitops/le.h
index d51beff60375..e3b0da9a25f1 100644
--- a/include/asm-generic/bitops/le.h
+++ b/include/asm-generic/bitops/le.h
@@ -16,47 +16,47 @@
 #endif
 
 
-static inline int test_bit_le(int nr, const void *addr)
+static inline int test_bit_le(unsigned long nr, const void *addr)
 {
 	return test_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline void set_bit_le(int nr, void *addr)
+static inline void set_bit_le(unsigned long nr, void *addr)
 {
 	set_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline void clear_bit_le(int nr, void *addr)
+static inline void clear_bit_le(unsigned long nr, void *addr)
 {
 	clear_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline void __set_bit_le(int nr, void *addr)
+static inline void __set_bit_le(unsigned long nr, void *addr)
 {
 	__set_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline void __clear_bit_le(int nr, void *addr)
+static inline void __clear_bit_le(unsigned long nr, void *addr)
 {
 	__clear_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline int test_and_set_bit_le(int nr, void *addr)
+static inline int test_and_set_bit_le(unsigned long nr, void *addr)
 {
 	return test_and_set_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline int test_and_clear_bit_le(int nr, void *addr)
+static inline int test_and_clear_bit_le(unsigned long nr, void *addr)
 {
 	return test_and_clear_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline int __test_and_set_bit_le(int nr, void *addr)
+static inline int __test_and_set_bit_le(unsigned long nr, void *addr)
 {
 	return __test_and_set_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
 
-static inline int __test_and_clear_bit_le(int nr, void *addr)
+static inline int __test_and_clear_bit_le(unsigned long nr, void *addr)
 {
 	return __test_and_clear_bit(nr ^ BITOP_LE_SWIZZLE, addr);
 }
-- 
2.53.0