On Thu, Apr 30, 2020 at 10:25:18AM +0530, Ritesh Harjani wrote:
> We better warn the fibmap user and not return a truncated and therefore
> an incorrect block map address if the bmap() returned block address
> is greater than INT_MAX (since user supplied integer pointer).
>
> It's better to pr_warn() all user of ioctl_fibmap() and return a proper
> error code rather than silently letting a FS corruption happen if the
> user tries to fiddle around with the returned block map address.
>
> We fix this by returning an error code of -ERANGE and returning 0 as the
> block mapping address in case if it is > INT_MAX.
>
> Now iomap_bmap() could be called from either of these two paths.
> Either when a user is calling an ioctl_fibmap() interface to get
> the block mapping address or by some filesystem via use of bmap()
> internal kernel API.
> bmap() kernel API is well equipped with handling of u64 addresses.
>
> WARN condition in iomap_bmap_actor() was mainly added to warn all
> the fibmap users. But now that we have directly added this warning
> for all fibmap users and also made sure to return 0 as block map address
> in case if addr > INT_MAX.
> So we can now remove this logic from iomap_bmap_actor().
>
> Signed-off-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
Looks good to me,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> v2 -> v3:
> 1. Added file path info using (%pD4)
> 2. Dropped Reviewed-by tags for reviewing this final version.
>
> fs/ioctl.c | 8 ++++++++
> fs/iomap/fiemap.c | 5 +----
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index f1d93263186c..6b8629fbe0fd 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -55,6 +55,7 @@ EXPORT_SYMBOL(vfs_ioctl);
> static int ioctl_fibmap(struct file *filp, int __user *p)
> {
> struct inode *inode = file_inode(filp);
> + struct super_block *sb = inode->i_sb;
> int error, ur_block;
> sector_t block;
>
> @@ -71,6 +72,13 @@ static int ioctl_fibmap(struct file *filp, int __user *p)
> block = ur_block;
> error = bmap(inode, &block);
>
> + if (block > INT_MAX) {
> + error = -ERANGE;
> + pr_warn_ratelimited("[%s/%d] FS: %s File: %pD4 would truncate fibmap result\n",
> + current->comm, task_pid_nr(current),
> + sb->s_id, filp);
> + }
> +
> if (error)
> ur_block = 0;
> else
> diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
> index bccf305ea9ce..d55e8f491a5e 100644
> --- a/fs/iomap/fiemap.c
> +++ b/fs/iomap/fiemap.c
> @@ -117,10 +117,7 @@ iomap_bmap_actor(struct inode *inode, loff_t pos, loff_t length,
>
> if (iomap->type == IOMAP_MAPPED) {
> addr = (pos - iomap->offset + iomap->addr) >> inode->i_blkbits;
> - if (addr > INT_MAX)
> - WARN(1, "would truncate bmap result\n");
> - else
> - *bno = addr;
> + *bno = addr;
> }
> return 0;
> }
> --
> 2.21.0
>
