2020-04-12 09:25:14

by Ritesh Harjani

Subject: [RFC 1/1] ext4: Fix overflow case for map.m_len in ext4_iomap_begin_*

EXT4_MAX_LOGICAL_BLOCK - map.m_lblk + 1 in case when
map.m_lblk (offset) is 0 could overflow an unsigned int
and become 0.

Fix this.

Signed-off-by: Ritesh Harjani <[email protected]>
Reported-by: [email protected]
Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
---
fs/ext4/inode.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e416096fc081..d630ec7a9c8e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3424,6 +3424,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
int ret;
struct ext4_map_blocks map;
u8 blkbits = inode->i_blkbits;
+ loff_t len;

if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
return -EINVAL;
@@ -3435,8 +3436,11 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
* Calculate the first and last logical blocks respectively.
*/
map.m_lblk = offset >> blkbits;
- map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
+ len = min_t(loff_t, (offset + length - 1) >> blkbits,
EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
+ if (len > EXT4_MAX_LOGICAL_BLOCK)
+ len = EXT4_MAX_LOGICAL_BLOCK;
+ map.m_len = len;

if (flags & IOMAP_WRITE)
ret = ext4_iomap_alloc(inode, &map, flags);
@@ -3524,6 +3528,7 @@ static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
bool delalloc = false;
struct ext4_map_blocks map;
u8 blkbits = inode->i_blkbits;
+ loff_t len

if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
return -EINVAL;
@@ -3541,8 +3546,11 @@ static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
* Calculate the first and last logical block respectively.
*/
map.m_lblk = offset >> blkbits;
- map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
+ len = min_t(loff_t, (offset + length - 1) >> blkbits,
EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
+ if (len > EXT4_MAX_LOGICAL_BLOCK)
+ len = EXT4_MAX_LOGICAL_BLOCK;
+ map.m_len = len;

/*
* Fiemap callers may call for offset beyond s_bitmap_maxbytes.
--
2.21.0

2020-04-15 21:44:04

by Jan Kara

Subject: Re: [RFC 1/1] ext4: Fix overflow case for map.m_len in ext4_iomap_begin_*

On Sun 12-04-20 14:54:35, Ritesh Harjani wrote:
> EXT4_MAX_LOGICAL_BLOCK - map.m_lblk + 1 in case when
> map.m_lblk (offset) is 0 could overflow an unsigned int
> and become 0.
>
> Fix this.
>
> Signed-off-by: Ritesh Harjani <[email protected]>
> Reported-by: [email protected]
> Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")

The patch looks good to me. You can add:

Reviewed-by: Jan Kara <[email protected]>

Honza

> ---
> fs/ext4/inode.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index e416096fc081..d630ec7a9c8e 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3424,6 +3424,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> int ret;
> struct ext4_map_blocks map;
> u8 blkbits = inode->i_blkbits;
> + loff_t len;
>
> if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
> return -EINVAL;
> @@ -3435,8 +3436,11 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> * Calculate the first and last logical blocks respectively.
> */
> map.m_lblk = offset >> blkbits;
> - map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
> + len = min_t(loff_t, (offset + length - 1) >> blkbits,
> EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
> + if (len > EXT4_MAX_LOGICAL_BLOCK)
> + len = EXT4_MAX_LOGICAL_BLOCK;
> + map.m_len = len;
>
> if (flags & IOMAP_WRITE)
> ret = ext4_iomap_alloc(inode, &map, flags);
> @@ -3524,6 +3528,7 @@ static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
> bool delalloc = false;
> struct ext4_map_blocks map;
> u8 blkbits = inode->i_blkbits;
> + loff_t len
>
> if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
> return -EINVAL;
> @@ -3541,8 +3546,11 @@ static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
> * Calculate the first and last logical block respectively.
> */
> map.m_lblk = offset >> blkbits;
> - map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
> + len = min_t(loff_t, (offset + length - 1) >> blkbits,
> EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
> + if (len > EXT4_MAX_LOGICAL_BLOCK)
> + len = EXT4_MAX_LOGICAL_BLOCK;
> + map.m_len = len;
>
> /*
> * Fiemap callers may call for offset beyond s_bitmap_maxbytes.
> --
> 2.21.0
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

2020-04-16 07:40:01

by Ritesh Harjani

Subject: Re: [RFC 1/1] ext4: Fix overflow case for map.m_len in ext4_iomap_begin_*

Sorry Jan and others. Please ignore this patch.
I will resend a proper one after making sure it is tested via syzbot.

On 4/14/20 9:20 PM, Jan Kara wrote:
> On Sun 12-04-20 14:54:35, Ritesh Harjani wrote:
>> EXT4_MAX_LOGICAL_BLOCK - map.m_lblk + 1 in case when
>> map.m_lblk (offset) is 0 could overflow an unsigned int
>> and become 0.
>>
>> Fix this.
>>
>> Signed-off-by: Ritesh Harjani <[email protected]>
>> Reported-by: [email protected]
>> Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
>
> The patch looks good to me. You can add:
>
> Reviewed-by: Jan Kara <[email protected]>
>
> Honza
>
>> ---
>> fs/ext4/inode.c | 12 ++++++++++--
>> 1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index e416096fc081..d630ec7a9c8e 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -3424,6 +3424,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
>> int ret;
>> struct ext4_map_blocks map;
>> u8 blkbits = inode->i_blkbits;
>> + loff_t len;
>>
>> if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
>> return -EINVAL;
>> @@ -3435,8 +3436,11 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
>> * Calculate the first and last logical blocks respectively.
>> */
>> map.m_lblk = offset >> blkbits;
>> - map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
>> + len = min_t(loff_t, (offset + length - 1) >> blkbits,
>> EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
>> + if (len > EXT4_MAX_LOGICAL_BLOCK)
>> + len = EXT4_MAX_LOGICAL_BLOCK;
>> + map.m_len = len;
>>
>> if (flags & IOMAP_WRITE)
>> ret = ext4_iomap_alloc(inode, &map, flags);
>> @@ -3524,6 +3528,7 @@ static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
>> bool delalloc = false;
>> struct ext4_map_blocks map;
>> u8 blkbits = inode->i_blkbits;
>> + loff_t len
>>
>> if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
>> return -EINVAL;
>> @@ -3541,8 +3546,11 @@ static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
>> * Calculate the first and last logical block respectively.
>> */
>> map.m_lblk = offset >> blkbits;
>> - map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
>> + len = min_t(loff_t, (offset + length - 1) >> blkbits,
>> EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
>> + if (len > EXT4_MAX_LOGICAL_BLOCK)
>> + len = EXT4_MAX_LOGICAL_BLOCK;
>> + map.m_len = len;
>>
>> /*
>> * Fiemap callers may call for offset beyond s_bitmap_maxbytes.
>> --
>> 2.21.0
>>