We need to check that userspace callers can only truncate preallocated
blocks from files they have write access to to prevent them from prematurley
reclaiming blocks from another user. The internal reclaimer will not specify
the XFS_EOF_FLAGS_PERM_CHECK flag, but userspace callers should.
Add check for read-only filesystem to free eofblocks ioctl.
Signed-off-by: Dwight Engen <dwight.engen@xxxxxxxxxx>
---
fs/xfs/xfs_fs.h | 1 +
fs/xfs/xfs_icache.c | 4 ++++
fs/xfs/xfs_ioctl.c | 4 ++++
3 files changed, 9 insertions(+)
diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
index 7eb4a5e..aee4b12 100644
--- a/fs/xfs/xfs_fs.h
+++ b/fs/xfs/xfs_fs.h
@@ -361,6 +361,7 @@ struct xfs_fs_eofblocks {
#define XFS_EOF_FLAGS_GID (1 << 2) /* filter by gid */
#define XFS_EOF_FLAGS_PRID (1 << 3) /* filter by project id */
#define XFS_EOF_FLAGS_MINFILESIZE (1 << 4) /* filter by min file size */
+#define XFS_EOF_FLAGS_PERM_CHECK (1 << 5) /* check can write inode */
#define XFS_EOF_FLAGS_VALID \
(XFS_EOF_FLAGS_SYNC | \
XFS_EOF_FLAGS_UID | \
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index ed35584..823f2c0 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1247,6 +1247,10 @@ xfs_inode_free_eofblocks(
if (!xfs_inode_match_id(ip, eofb))
return 0;
+ if ((eofb->eof_flags & XFS_EOF_FLAGS_PERM_CHECK) &&
+ inode_permission(VFS_I(ip), MAY_WRITE))
+ return 0;
+
/* skip the inode if the file size is too small */
if (eofb->eof_flags & XFS_EOF_FLAGS_MINFILESIZE &&
XFS_ISIZE(ip) < eofb->eof_min_file_size)
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index ecab261..c7cb632 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1613,6 +1613,9 @@ xfs_file_ioctl(
struct xfs_fs_eofblocks eofb;
struct xfs_eofblocks keofb;
+ if (IS_RDONLY(inode))
+ return -XFS_ERROR(EROFS);
+
if (copy_from_user(&eofb, arg, sizeof(eofb)))
return -XFS_ERROR(EFAULT);
@@ -1630,6 +1633,7 @@ xfs_file_ioctl(
if (error)
return -error;
+ keofb.eof_flags |= XFS_EOF_FLAGS_PERM_CHECK;
return -xfs_icache_free_eofblocks(mp, &keofb);
}
--
1.8.1.4
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