[RFC,1/1] ext4: Fix overflow case for map.m_len in ext4_iomap_begin_*
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Message ID dea98f0b07e16de219d8741c1fefc7cb476cb482.1586681010.git.riteshh@linux.ibm.com
State New
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Series
  • [RFC,1/1] ext4: Fix overflow case for map.m_len in ext4_iomap_begin_*
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Commit Message

Ritesh Harjani April 12, 2020, 9:24 a.m. UTC
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 <riteshh@linux.ibm.com>
Reported-by: syzbot+77fa5bdb65cc39711820@syzkaller.appspotmail.com
Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
---
 fs/ext4/inode.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

Comments

Jan Kara April 14, 2020, 3:50 p.m. UTC | #1
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 <riteshh@linux.ibm.com>
> Reported-by: syzbot+77fa5bdb65cc39711820@syzkaller.appspotmail.com
> Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")

The patch looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								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
>
Ritesh Harjani April 16, 2020, 7:38 a.m. UTC | #2
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 <riteshh@linux.ibm.com>
>> Reported-by: syzbot+77fa5bdb65cc39711820@syzkaller.appspotmail.com
>> Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
> 
> The patch looks good to me. You can add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> 								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
>>

Patch
diff mbox series

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.