| Message ID | 20221110031024.204-1-thunder.leizhen@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fs: Clear a UBSAN shift-out-of-bounds warning | expand |
On Thu, Nov 10, 2022 at 11:10:24AM +0800, Zhen Lei wrote: > UBSAN: shift-out-of-bounds in fs/locks.c:2572:16 > left shift of 1 by 63 places cannot be represented in type 'long long int' > > Switch the calculation method to ((quarter - 1) * 2 + 1) can help us > eliminate this false positive. > > On the other hand, the old implementation has problems with char and > short types, although not currently involved. > printf("%d: %x\n", sizeof(char), INT_LIMIT(char)); > printf("%d: %x\n", sizeof(short), INT_LIMIT(short)); > 1: ffffff7f > 2: ffff7fff > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > --- > include/linux/fs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index e654435f16512c1..88d42e2daed9f6c 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1131,7 +1131,7 @@ struct file_lock_context { > > /* The following constant reflects the upper bound of the file/locking space */ > #ifndef OFFSET_MAX > -#define INT_LIMIT(x) (~((x)1 << (sizeof(x)*8 - 1))) > +#define INT_LIMIT(x) ((((x)1 << (sizeof(x) * 8 - 2)) - 1) * 2 + 1) > #define OFFSET_MAX INT_LIMIT(loff_t) > #define OFFT_OFFSET_MAX INT_LIMIT(off_t) > #endif This problem has already been solved by type_max() in include/linux/overflow.h. How about removing INT_LIMIT() and using type_max() instead? - Eric
On 2022/11/20 3:39, Eric Biggers wrote: > On Thu, Nov 10, 2022 at 11:10:24AM +0800, Zhen Lei wrote: >> UBSAN: shift-out-of-bounds in fs/locks.c:2572:16 >> left shift of 1 by 63 places cannot be represented in type 'long long int' >> >> Switch the calculation method to ((quarter - 1) * 2 + 1) can help us >> eliminate this false positive. >> >> On the other hand, the old implementation has problems with char and >> short types, although not currently involved. >> printf("%d: %x\n", sizeof(char), INT_LIMIT(char)); >> printf("%d: %x\n", sizeof(short), INT_LIMIT(short)); >> 1: ffffff7f >> 2: ffff7fff >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> --- >> include/linux/fs.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/linux/fs.h b/include/linux/fs.h >> index e654435f16512c1..88d42e2daed9f6c 100644 >> --- a/include/linux/fs.h >> +++ b/include/linux/fs.h >> @@ -1131,7 +1131,7 @@ struct file_lock_context { >> >> /* The following constant reflects the upper bound of the file/locking space */ >> #ifndef OFFSET_MAX >> -#define INT_LIMIT(x) (~((x)1 << (sizeof(x)*8 - 1))) >> +#define INT_LIMIT(x) ((((x)1 << (sizeof(x) * 8 - 2)) - 1) * 2 + 1) >> #define OFFSET_MAX INT_LIMIT(loff_t) >> #define OFFT_OFFSET_MAX INT_LIMIT(off_t) >> #endif > > This problem has already been solved by type_max() in include/linux/overflow.h. > How about removing INT_LIMIT() and using type_max() instead? It's better to use type_max(). INT_LIMIT() is currently valid only for signed type. Besides, my method is actually the same as type_max(). Using type_max() does not result in code duplication. > > - Eric > . >
diff --git a/include/linux/fs.h b/include/linux/fs.h index e654435f16512c1..88d42e2daed9f6c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1131,7 +1131,7 @@ struct file_lock_context { /* The following constant reflects the upper bound of the file/locking space */ #ifndef OFFSET_MAX -#define INT_LIMIT(x) (~((x)1 << (sizeof(x)*8 - 1))) +#define INT_LIMIT(x) ((((x)1 << (sizeof(x) * 8 - 2)) - 1) * 2 + 1) #define OFFSET_MAX INT_LIMIT(loff_t) #define OFFT_OFFSET_MAX INT_LIMIT(off_t) #endif
UBSAN: shift-out-of-bounds in fs/locks.c:2572:16 left shift of 1 by 63 places cannot be represented in type 'long long int' Switch the calculation method to ((quarter - 1) * 2 + 1) can help us eliminate this false positive. On the other hand, the old implementation has problems with char and short types, although not currently involved. printf("%d: %x\n", sizeof(char), INT_LIMIT(char)); printf("%d: %x\n", sizeof(short), INT_LIMIT(short)); 1: ffffff7f 2: ffff7fff Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- include/linux/fs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)