An overflow may occur if the function is called with the last
block and an offset greater than zero. It is necessary to add
a check to avoid this.
Found by Linux Verification Center (linuxtesting.org) with Svace.
Signed-off-by: Roman Smirnov <[email protected]>
---
fs/udf/balloc.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
index ab3ffc355949..cd83bbc7d890 100644
--- a/fs/udf/balloc.c
+++ b/fs/udf/balloc.c
@@ -151,6 +151,13 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
block = bloc->logicalBlockNum + offset +
(sizeof(struct spaceBitmapDesc) << 3);
+ if (block < offset + (sizeof(struct spaceBitmapDesc) << 3)) {
+ udf_debug("integer overflow: %u + %u + %zu",
+ bloc->logicalBlockNum, offset,
+ sizeof(struct spaceBitmapDesc) << 3);
+ goto error_return;
+ }
+
do {
overflow = 0;
block_group = block >> (sb->s_blocksize_bits + 3);
--
2.34.1
On 6/10/24 10:25 AM, Roman Smirnov wrote:
> An overflow may occur if the function is called with the last
> block and an offset greater than zero. It is necessary to add
> a check to avoid this.
>
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Signed-off-by: Roman Smirnov <[email protected]>
> ---
> fs/udf/balloc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
> index ab3ffc355949..cd83bbc7d890 100644
> --- a/fs/udf/balloc.c
> +++ b/fs/udf/balloc.c
> @@ -151,6 +151,13 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
> block = bloc->logicalBlockNum + offset +
> (sizeof(struct spaceBitmapDesc) << 3);
Hm, I can't say I understand this code well... Is the block variable here
counted in blocks or bytes?
>
As I've already said, we hardly need an empty line here -- just
don't add an empty line after your *if*...
> + if (block < offset + (sizeof(struct spaceBitmapDesc) << 3)) {
Thinking about this again, this addition may overflow 32 bits as well,
so it's better to compare with block with bloc->logicalBlockNum...
[...]
MBR, Sergey
On 6/10/24 10:25 AM, Roman Smirnov wrote:
> An overflow may occur if the function is called with the last
> block and an offset greater than zero. It is necessary to add
> a check to avoid this.
>
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Signed-off-by: Roman Smirnov <[email protected]>
> ---
> fs/udf/balloc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
> index ab3ffc355949..cd83bbc7d890 100644
> --- a/fs/udf/balloc.c
> +++ b/fs/udf/balloc.c
> @@ -151,6 +151,13 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
> block = bloc->logicalBlockNum + offset +
> (sizeof(struct spaceBitmapDesc) << 3);
Hm, I can't say I understand this code well... Is the block variable here
counted in blocks or bytes?
>
As I've already said, we hardly need an empty line here -- just
don't add an empty line after your *if*...
> + if (block < offset + (sizeof(struct spaceBitmapDesc) << 3)) {
Thinking about this again, this addition may overflow 32 bits as well,
so it's better to compare block with bloc->logicalBlockNum...
[...]
MBR, Sergey
On Mon 10-06-24 10:25:22, Roman Smirnov wrote:
> An overflow may occur if the function is called with the last
> block and an offset greater than zero. It is necessary to add
> a check to avoid this.
>
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Signed-off-by: Roman Smirnov <[email protected]>
Thanks for the patch! Actually there are overflow checks just a few lines
above the place you modify:
if (bloc->logicalBlockNum + count < count ||
(bloc->logicalBlockNum + count) > partmap->s_partition_len) {
So please update those to take 'offset' into account instead. Also please
use check_add_overflow() for the integer overflow check.
Honza
> ---
> fs/udf/balloc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
> index ab3ffc355949..cd83bbc7d890 100644
> --- a/fs/udf/balloc.c
> +++ b/fs/udf/balloc.c
> @@ -151,6 +151,13 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
> block = bloc->logicalBlockNum + offset +
> (sizeof(struct spaceBitmapDesc) << 3);
>
> + if (block < offset + (sizeof(struct spaceBitmapDesc) << 3)) {
> + udf_debug("integer overflow: %u + %u + %zu",
> + bloc->logicalBlockNum, offset,
> + sizeof(struct spaceBitmapDesc) << 3);
> + goto error_return;
> + }
> +
> do {
> overflow = 0;
> block_group = block >> (sb->s_blocksize_bits + 3);
> --
> 2.34.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR