Re: [PATCH 08/11] fs: move fiemap range validation into the file systems instances

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On 4/27/20 11:49 PM, Christoph Hellwig wrote:
Replace fiemap_check_flags with a fiemap_validate helpers that also takes
the inode and mapped range, and performs the sanity check and truncation
previously done in fiemap_check_range.  This way the validation is inside
the file system itself and thus properly works for the stacked overlayfs
case as well.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
  Documentation/filesystems/fiemap.txt |  8 ++---
  fs/btrfs/inode.c                     |  2 +-
  fs/cifs/smb2ops.c                    |  6 ++--
  fs/ext4/extents.c                    |  5 +--
  fs/f2fs/data.c                       |  3 +-
  fs/ioctl.c                           | 53 +++++++++++-----------------
  fs/iomap/fiemap.c                    |  2 +-
  fs/nilfs2/inode.c                    |  2 +-
  fs/ocfs2/extent_map.c                |  3 +-
  include/linux/fiemap.h               |  3 +-
  10 files changed, 40 insertions(+), 47 deletions(-)

diff --git a/Documentation/filesystems/fiemap.txt b/Documentation/filesystems/fiemap.txt
index ac87e6fda842b..05926b7f92809 100644
--- a/Documentation/filesystems/fiemap.txt
+++ b/Documentation/filesystems/fiemap.txt
@@ -203,15 +203,13 @@ EINTR once fatal signal received.
Flag checking should be done at the beginning of the ->fiemap callback via the
-fiemap_check_flags() helper:
-
-int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
+fiemap_prep() helper.

Let's add the fiemap_prep() function prototype here.
So that below description would make more sense.

The struct fieinfo should be passed in as received from ioctl_fiemap(). The
  set of fiemap flags which the fs understands should be passed via fs_flags. If
-fiemap_check_flags finds invalid user flags, it will place the bad values in
+fiemap_prep finds invalid user flags, it will place the bad values in
  fieinfo->fi_flags and return -EBADR. If the file system gets -EBADR, from
-fiemap_check_flags(), it should immediately exit, returning that error back to
+fiemap_prep(), it should immediately exit, returning that error back to
  ioctl_fiemap().

Also maybe we should also add more info about fiemap_prep() helper.
Since it also checks for invalid len and invalid start range and hence
could return -EINVAL or -EFBIG.


diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 320d1062068d3..1f1ec361089b3 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8250,7 +8250,7 @@ static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  {
  	int	ret;
- ret = fiemap_check_flags(fieinfo, BTRFS_FIEMAP_FLAGS);
+	ret = fiemap_prep(inode, fieinfo, start, &len, BTRFS_FIEMAP_FLAGS);
  	if (ret)
  		return ret;
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 09047f1ddfb66..8a2e94931dc96 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3408,8 +3408,10 @@ static int smb3_fiemap(struct cifs_tcon *tcon,
  	int i, num, rc, flags, last_blob;
  	u64 next;
- if (fiemap_check_flags(fei, FIEMAP_FLAG_SYNC))
-		return -EBADR;
+	rc = fiemap_prep(cfile->dentry->d_inode, fei, start, &len,
+			FIEMAP_FLAG_SYNC);

How about d_inode(cfile->dentry) ?


+	if (rc)
+		rc;

missed "return rc" here?



xid = get_xid();
   again:
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index a41ae7c510170..41f73dea92cac 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4908,8 +4908,9 @@ int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE;
  	}
- if (fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC))
-		return -EBADR;
+	error = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_SYNC);
+	if (error)
+		return error;
error = ext4_fiemap_check_ranges(inode, start, &len);
  	if (error)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 25abbbb65ba09..03faafc591b17 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1825,7 +1825,8 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  			return ret;
  	}
- ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR);
+	ret = fiemap_prep(inode, fieinfo, start, &len,
+			FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR);
  	if (ret)
  		return ret;
diff --git a/fs/ioctl.c b/fs/ioctl.c
index cbc84e23d00bd..4d94c20c9596b 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -141,9 +141,12 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical,
  EXPORT_SYMBOL(fiemap_fill_next_extent);
/**
- * fiemap_check_flags - check validity of requested flags for fiemap
+ * fiemap_prep - check validity of requested flags for fiemap
+ * @inode:	Inode to operate on
   * @fieinfo:	Fiemap context passed into ->fiemap
- * @fs_flags:	Set of fiemap flags that the file system understands
+ * @start:	Start of the mapped range
+ * @len:	Length of the mapped range, can be truncated by this function.
+ * @supported_flags:	Set of fiemap flags that the file system understands
   *
   * Called from file system ->fiemap callback. This will compute the
   * intersection of valid fiemap flags and those that the fs supports. That

Let's also add more documentation about this new fiemap_prep() helper.
Earlier comments above this function description only talks about
incompat flags. We should add more info about check_ranges part as well here.


@@ -154,48 +157,38 @@ EXPORT_SYMBOL(fiemap_fill_next_extent);
   *
   * Returns 0 on success, -EBADR on bad flags.
   */

Also let's add ", -EINVAL or -EFBIG on invalid len or start range
respectively"


-int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags)
+int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		u64 start, u64 *len, u32 supported_flags)
  {
+	u64 maxbytes = inode->i_sb->s_maxbytes;
  	u32 incompat_flags;
- incompat_flags = fieinfo->fi_flags & ~(FIEMAP_FLAGS_COMPAT & fs_flags);
-	if (incompat_flags) {
-		fieinfo->fi_flags = incompat_flags;
-		return -EBADR;
-	}
-	return 0;
-}
-EXPORT_SYMBOL(fiemap_check_flags);
-
-static int fiemap_check_ranges(struct super_block *sb,
-			       u64 start, u64 len, u64 *new_len)
-{
-	u64 maxbytes = (u64) sb->s_maxbytes;
-
-	*new_len = len;
-
-	if (len == 0)
+	if (*len == 0)
  		return -EINVAL;
-
  	if (start > maxbytes)
  		return -EFBIG;
/*
  	 * Shrink request scope to what the fs can actually handle.
  	 */
-	if (len > maxbytes || (maxbytes - len) < start)
-		*new_len = maxbytes - start;
+	if (*len > maxbytes || (maxbytes - *len) < start)
+		*len = maxbytes - start;
+ supported_flags &= FIEMAP_FLAGS_COMPAT;
+	incompat_flags = fieinfo->fi_flags & ~supported_flags;
+	if (incompat_flags) {
+		fieinfo->fi_flags = incompat_flags;
+		return -EBADR;
+	}
  	return 0;
  }
+EXPORT_SYMBOL(fiemap_prep);
static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
  {
  	struct fiemap fiemap;
  	struct fiemap_extent_info fieinfo = { 0, };
  	struct inode *inode = file_inode(filp);
-	struct super_block *sb = inode->i_sb;
-	u64 len;
  	int error;
if (!inode->i_op->fiemap)
@@ -207,11 +200,6 @@ static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
  	if (fiemap.fm_extent_count > FIEMAP_MAX_EXTENTS)
  		return -EINVAL;
- error = fiemap_check_ranges(sb, fiemap.fm_start, fiemap.fm_length,
-				    &len);
-	if (error)
-		return error;
-
  	fieinfo.fi_flags = fiemap.fm_flags;
  	fieinfo.fi_extents_max = fiemap.fm_extent_count;
  	fieinfo.fi_extents_start = ufiemap->fm_extents;
@@ -224,7 +212,8 @@ static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
  	if (fieinfo.fi_flags & FIEMAP_FLAG_SYNC)
  		filemap_write_and_wait(inode->i_mapping);
- error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start, len);
+	error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start,
+			fiemap.fm_length);
  	fiemap.fm_flags = fieinfo.fi_flags;
  	fiemap.fm_mapped_extents = fieinfo.fi_extents_mapped;
  	if (copy_to_user(ufiemap, &fiemap, sizeof(fiemap)))
@@ -312,7 +301,7 @@ static int __generic_block_fiemap(struct inode *inode,
  	bool past_eof = false, whole_file = false;
  	int ret = 0;
- ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC);
+	ret = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_SYNC);
  	if (ret)
  		return ret;
diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
index dd04e4added15..5e4e3520424da 100644
--- a/fs/iomap/fiemap.c
+++ b/fs/iomap/fiemap.c
@@ -75,7 +75,7 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
  	ctx.fi = fi;
  	ctx.prev.type = IOMAP_HOLE;
- ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
+	ret = fiemap_prep(inode, fi, start, &len, FIEMAP_FLAG_SYNC);
  	if (ret)
  		return ret;
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 6e1aca38931f3..052c2da11e4d7 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -1006,7 +1006,7 @@ int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  	unsigned int blkbits = inode->i_blkbits;
  	int ret, n;
- ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC);
+	ret = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_SYNC);
  	if (ret)
  		return ret;
diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index e3e2d1b2af51a..3744179b73fa1 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -746,7 +746,8 @@ int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  	struct buffer_head *di_bh = NULL;
  	struct ocfs2_extent_rec rec;
- ret = fiemap_check_flags(fieinfo, OCFS2_FIEMAP_FLAGS);
+	ret = fiemap_prep(inode, fieinfo, map_start, &map_len,
+			OCFS2_FIEMAP_FLAGS);
  	if (ret)
  		return ret;
diff --git a/include/linux/fiemap.h b/include/linux/fiemap.h
index 240d4f7d9116a..4e624c4665837 100644
--- a/include/linux/fiemap.h
+++ b/include/linux/fiemap.h
@@ -13,9 +13,10 @@ struct fiemap_extent_info {
  							fiemap_extent array */
  };
+int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		u64 start, u64 *len, u32 supported_flags);
  int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
  			    u64 phys, u64 len, u32 flags);
-int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);

While we are at it, could remove this above additional line as well.

  int generic_block_fiemap(struct inode *inode,
  		struct fiemap_extent_info *fieinfo, u64 start, u64 len,




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