| Message ID | 20240123002814.1396804-76-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
On Mon 22-01-24 16:27:51, Kees Cook wrote: > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow(). > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Jan Kara <jack@suse.com> > Signed-off-by: Kees Cook <keescook@chromium.org> Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/udf/balloc.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c > index ab3ffc355949..5c88300c3de7 100644 > --- a/fs/udf/balloc.c > +++ b/fs/udf/balloc.c > @@ -139,7 +139,7 @@ static void udf_bitmap_free_blocks(struct super_block *sb, > > mutex_lock(&sbi->s_alloc_mutex); > partmap = &sbi->s_partmaps[bloc->partitionReferenceNum]; > - if (bloc->logicalBlockNum + count < count || > + if (add_would_overflow(count, bloc->logicalBlockNum) || > (bloc->logicalBlockNum + count) > partmap->s_partition_len) { > udf_debug("%u < %d || %u + %u > %u\n", > bloc->logicalBlockNum, 0, > @@ -390,7 +390,7 @@ static void udf_table_free_blocks(struct super_block *sb, > > mutex_lock(&sbi->s_alloc_mutex); > partmap = &sbi->s_partmaps[bloc->partitionReferenceNum]; > - if (bloc->logicalBlockNum + count < count || > + if (add_would_overflow(count, bloc->logicalBlockNum) || > (bloc->logicalBlockNum + count) > partmap->s_partition_len) { > udf_debug("%u < %d || %u + %u > %u\n", > bloc->logicalBlockNum, 0, > -- > 2.34.1 >
diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c index ab3ffc355949..5c88300c3de7 100644 --- a/fs/udf/balloc.c +++ b/fs/udf/balloc.c @@ -139,7 +139,7 @@ static void udf_bitmap_free_blocks(struct super_block *sb, mutex_lock(&sbi->s_alloc_mutex); partmap = &sbi->s_partmaps[bloc->partitionReferenceNum]; - if (bloc->logicalBlockNum + count < count || + if (add_would_overflow(count, bloc->logicalBlockNum) || (bloc->logicalBlockNum + count) > partmap->s_partition_len) { udf_debug("%u < %d || %u + %u > %u\n", bloc->logicalBlockNum, 0, @@ -390,7 +390,7 @@ static void udf_table_free_blocks(struct super_block *sb, mutex_lock(&sbi->s_alloc_mutex); partmap = &sbi->s_partmaps[bloc->partitionReferenceNum]; - if (bloc->logicalBlockNum + count < count || + if (add_would_overflow(count, bloc->logicalBlockNum) || (bloc->logicalBlockNum + count) > partmap->s_partition_len) { udf_debug("%u < %d || %u + %u > %u\n", bloc->logicalBlockNum, 0,
In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Jan Kara <jack@suse.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/udf/balloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)