[PATCH] ext4: fix possible overflow in ext4_trim_fs()

[PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Lukas Czerner]

When determining last group through ext4_get_group_no_and_offset() the
result may be wrong in cases when range->start and range-len are too
big, because it may overflow when summing up those two numbers.

Fix that by checking range->len and limit its value to
ext4_blocks_count(). This commit was tested by myself with expected
result.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 fs/ext4/mballoc.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 5b4d4e3..7b05d92 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4819,6 +4819,7 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
 	ext4_group_t group, ngroups = ext4_get_groups_count(sb);
 	ext4_grpblk_t cnt = 0, first_block, last_block;
 	uint64_t start, len, minlen, trimmed;
+	ext4_fsblk_t blocks_count = ext4_blocks_count(EXT4_SB(sb)->s_es);
 	int ret = 0;
 
 	start = range->start >> sb->s_blocksize_bits;
@@ -4826,6 +4827,9 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
 	minlen = range->minlen >> sb->s_blocksize_bits;
 	trimmed = 0;
 
+	if (len > blocks_count)
+		len = blocks_count - start;
+
 	if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
 		return -EINVAL;
 
-- 
1.7.2.3

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Lukas Czerner]

On Thu, 25 Nov 2010, Lukas Czerner wrote:

> When determining last group through ext4_get_group_no_and_offset() the
> result may be wrong in cases when range->start and range-len are too
> big, because it may overflow when summing up those two numbers.
> 
> Fix that by checking range->len and limit its value to
> ext4_blocks_count(). This commit was tested by myself with expected
> result.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> ---
>  fs/ext4/mballoc.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 5b4d4e3..7b05d92 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4819,6 +4819,7 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
>  	ext4_group_t group, ngroups = ext4_get_groups_count(sb);
>  	ext4_grpblk_t cnt = 0, first_block, last_block;
>  	uint64_t start, len, minlen, trimmed;
> +	ext4_fsblk_t blocks_count = ext4_blocks_count(EXT4_SB(sb)->s_es);
>  	int ret = 0;
>  
>  	start = range->start >> sb->s_blocksize_bits;
> @@ -4826,6 +4827,9 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
>  	minlen = range->minlen >> sb->s_blocksize_bits;
>  	trimmed = 0;
>  
> +	if (len > blocks_count)
> +		len = blocks_count - start;
> +
>  	if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
>  		return -EINVAL;
>  
> 

Hi Ted,

what is the status of this patch ?

-Lukas

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Ted Ts'o]

On Thu, Nov 25, 2010 at 03:11:17PM +0100, Lukas Czerner wrote:
> When determining last group through ext4_get_group_no_and_offset() the
> result may be wrong in cases when range->start and range-len are too
> big, because it may overflow when summing up those two numbers.
> 
> Fix that by checking range->len and limit its value to
> ext4_blocks_count(). This commit was tested by myself with expected
> result.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>

Added to the ext4 patch queue.  Thanks for the ping.

      	     	  		       	   - Ted

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Lukas Czerner]

On Mon, 20 Dec 2010, Ted Ts'o wrote:

> On Thu, Nov 25, 2010 at 03:11:17PM +0100, Lukas Czerner wrote:
> > When determining last group through ext4_get_group_no_and_offset() the
> > result may be wrong in cases when range->start and range-len are too
> > big, because it may overflow when summing up those two numbers.
> > 
> > Fix that by checking range->len and limit its value to
> > ext4_blocks_count(). This commit was tested by myself with expected
> > result.
> > 
> > Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> 
> Added to the ext4 patch queue.  Thanks for the ping.
> 
>       	     	  		       	   - Ted
> 

Hi Ted,

Actually the patch is not enough, there is still a possibility for
overflow to happen. Jan Kara notice the same bug in ext3 batched discard
implementation. I am sorry for this, I'll sen updated patch ASAP.

-Lukas

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Ted Ts'o]

On Mon, Jan 10, 2011 at 12:25:05PM +0100, Lukas Czerner wrote:
> 
> Actually the patch is not enough, there is still a possibility for
> overflow to happen. Jan Kara notice the same bug in ext3 batched discard
> implementation. I am sorry for this, I'll sen updated patch ASAP.
> 

This isn't a new patch, and not a replacement for the previous one,
correct?

						- Ted

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Lukas Czerner]

On Mon, 10 Jan 2011, Ted Ts'o wrote:

> On Mon, Jan 10, 2011 at 12:25:05PM +0100, Lukas Czerner wrote:
> > 
> > Actually the patch is not enough, there is still a possibility for
> > overflow to happen. Jan Kara notice the same bug in ext3 batched discard
> > implementation. I am sorry for this, I'll sen updated patch ASAP.
> > 
> 
> This isn't a new patch, and not a replacement for the previous one,
> correct?
> 
> 						- Ted
> 

It is the replacement for the previous one.

-Lukas

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Ted Ts'o]

On Mon, Jan 10, 2011 at 05:52:49PM +0100, Lukas Czerner wrote:
> 
> It is the replacement for the previous one.
> 

Ah, I see, I got it confused with another trim_fs patch.  I wish you
had sent this to me earlier, but ok, I'll fix it up.

    	      	    	     	     	  - Ted

Re: [PATCH] ext4: fix possible overflow in ext4_trim_fs()

[Lukas Czerner]

On Mon, 10 Jan 2011, Ted Ts'o wrote:

> On Mon, Jan 10, 2011 at 05:52:49PM +0100, Lukas Czerner wrote:
> > 
> > It is the replacement for the previous one.
> > 
> 
> Ah, I see, I got it confused with another trim_fs patch.  I wish you
> had sent this to me earlier, but ok, I'll fix it up.
> 
>     	      	    	     	     	  - Ted
> 

Yes, sorry about that and thanks.

-Lukas