loop: avoid out-of-range warning
PATCH 1/1 loop: avoid out-of-range warning
From: Arnd Bergmann <[email protected]>
clang warns that the sanity check for page size always succeeds when building with 64KB pages:
drivers/block/loop.c:282:27: error: result of comparison of constant 65536 with expression of type 'unsigned short' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
~~~~~ ^ ~~~~~~~~~There is nothing wrong here, so just shut up the check by changing the type of the bsize argument.
--- drivers/block/loop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/block/loop.c +1 -1
@@ -277,7 +277,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)* @bsize: size to validate */ static int -loop_validate_block_size (unsigned short bsize) +loop_validate_block_size (unsigned int bsize) {if (bsize <512 || bsize >PAGE_SIZE || !is_power_of_2 (bsize))return -EINVAL ;
Signature · 1 line
2.29.2
Thanks!
Quoted 7 lines · Arnd Bergmann
From: Arnd Bergmann <[email protected]>
clang warns that the sanity check for page size always succeeds when building with 64KB pages:
drivers/block/loop.c:282:27: error: result of comparison of constant 65536 with expression of type 'unsigned short' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
Quoted 8 lines
if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize)) ~~~~~ ^ ~~~~~~~~~There is nothing wrong here, so just shut up the check by changing the type of the bsize argument.
Fixes 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl")Signed-off-by Arnd Bergmann <[email protected]>
Quoted 20 lines
--- drivers/block/loop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)drivers/block/loop.c +1
-2@@ -277,7 +277,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)* @bsize: size to validate */ static int -loop_validate_block_size (unsigned short bsize) +loop_validate_block_size (unsigned int bsize) {if (bsize <512 || bsize >PAGE_SIZE || !is_power_of_2 (bsize))return -EINVAL ; --2.29.2
Well, you found a bug here.
lo_simple_ioctl(LOOP_SET_BLOCK_SIZE) passes "unsigned long arg" to loop_validate_block_size() via loop_set_block_size(), and uses only lower 32bits. "(lo->lo_queue->limits.logical_block_size == arg)" is failing to "return 0;" if lower 32bits are the same but higher 32bits are not 0. Shouldn't we also check that higher 32bits are 0, by either making loop_validate_block_size() to accept "unsigned long" or making loop_set_block_size() return -EINVAL if larger than UINT_MAX ?
Quoted 2 lines
There is nothing wrong here, so just shut up the check by changing the type of the bsize argument.
I think there is something wrong here.
Since "unsigned short bsize" checked only lower 16bits, a fuzzer can pass e.g. 0xDEAD0200 (which is not a is_power_of_2() 32bits value) to
blk_queue_logical_block_size(lo->lo_queue, arg); blk_queue_physical_block_size(lo->lo_queue, arg); blk_queue_io_min(lo->lo_queue, arg);
and confuse the system?