fuse2fs: fix gid inheritance on sgid parent directories

When a child file is created inside a setgid parent directory, the child
is supposed to inherit the gid of the parent, not the fsgid of the
creating process.  Fix this error, which was discovered by generic/633,
generic/696, and generic/697.

Cc: linux-ext4@vger.kernel.org # v1.43
Fixes: 81cbf1ef4f5dab ("misc: add fuse2fs, a FUSE server for e2fsprogs")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/175182663041.1984706.582232688757289460.stgit@frogsfrogsfrogs
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 86fef7765e5e4669a2fd647699beb58c40e5ff46..0e9576b6ca6aa742c6399ae0ad1603d3d0d39547 100644 (file)
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -1065,6 +1065,30 @@ static inline void fuse2fs_set_gid(struct ext2_inode_large *inode, gid_t gid)
        ext2fs_set_i_gid_high(*inode, gid >> 16);
 }
 
+static int fuse2fs_new_child_gid(struct fuse2fs *ff, ext2_ino_t parent,
+                                gid_t *gid, int *parent_sgid)
+{
+       struct ext2_inode_large inode;
+       struct fuse_context *ctxt = fuse_get_context();
+       errcode_t err;
+
+       err = fuse2fs_read_inode(ff->fs, parent, &inode);
+       if (err)
+               return translate_error(ff->fs, parent, err);
+
+       if (inode.i_mode & S_ISGID) {
+               if (parent_sgid)
+                       *parent_sgid = 1;
+               *gid = inode.i_gid;
+       } else {
+               if (parent_sgid)
+                       *parent_sgid = 0;
+               *gid = ctxt->gid;
+       }
+
+       return 0;
+}
+
 static int op_mknod(const char *path, mode_t mode, dev_t dev)
 {
        struct fuse_context *ctxt = fuse_get_context();
@@ -1076,6 +1100,7 @@ static int op_mknod(const char *path, mode_t mode, dev_t dev)
        char *node_name, a;
        int filetype;
        struct ext2_inode_large inode;
+       gid_t gid;
        int ret = 0;
 
        FUSE2FS_CHECK_CONTEXT(ff);
@@ -1128,6 +1153,10 @@ static int op_mknod(const char *path, mode_t mode, dev_t dev)
                goto out2;
        }
 
+       err = fuse2fs_new_child_gid(ff, parent, &gid, NULL);
+       if (err)
+               goto out2;
+
        err = ext2fs_new_inode(fs, parent, mode, 0, &child);
        if (err) {
                ret = translate_error(fs, 0, err);
@@ -1158,7 +1187,7 @@ static int op_mknod(const char *path, mode_t mode, dev_t dev)
        inode.i_extra_isize = sizeof(struct ext2_inode_large) -
                EXT2_GOOD_OLD_INODE_SIZE;
        fuse2fs_set_uid(&inode, ctxt->uid);
-       fuse2fs_set_gid(&inode, ctxt->gid);
+       fuse2fs_set_gid(&inode, gid);
 
        err = ext2fs_write_new_inode(fs, child, EXT2_INODE(&inode));
        if (err) {
@@ -1199,7 +1228,8 @@ static int op_mkdir(const char *path, mode_t mode)
        char *block;
        blk64_t blk;
        int ret = 0;
-       mode_t parent_sgid;
+       gid_t gid;
+       int parent_sgid;
 
        FUSE2FS_CHECK_CONTEXT(ff);
        fs = ff->fs;
@@ -1235,13 +1265,9 @@ static int op_mkdir(const char *path, mode_t mode)
        if (ret)
                goto out2;
 
-       /* Is the parent dir sgid? */
-       err = fuse2fs_read_inode(fs, parent, &inode);
-       if (err) {
-               ret = translate_error(fs, parent, err);
+       err = fuse2fs_new_child_gid(ff, parent, &gid, &parent_sgid);
+       if (err)
                goto out2;
-       }
-       parent_sgid = inode.i_mode & S_ISGID;
 
        *node_name = a;
 
@@ -1273,9 +1299,10 @@ static int op_mkdir(const char *path, mode_t mode)
        }
 
        fuse2fs_set_uid(&inode, ctxt->uid);
-       fuse2fs_set_gid(&inode, ctxt->gid);
-       inode.i_mode = LINUX_S_IFDIR | (mode & ~S_ISUID) |
-                      parent_sgid;
+       fuse2fs_set_gid(&inode, gid);
+       inode.i_mode = LINUX_S_IFDIR | (mode & ~S_ISUID);
+       if (parent_sgid)
+               inode.i_mode |= S_ISGID;
        inode.i_generation = ff->next_generation++;
        init_times(&inode);
 
@@ -1629,6 +1656,7 @@ static int op_symlink(const char *src, const char *dest)
        errcode_t err;
        char *node_name, a;
        struct ext2_inode_large inode;
+       gid_t gid;
        int ret = 0;
 
        FUSE2FS_CHECK_CONTEXT(ff);
@@ -1661,6 +1689,9 @@ static int op_symlink(const char *src, const char *dest)
        if (ret)
                goto out2;
 
+       err = fuse2fs_new_child_gid(ff, parent, &gid, NULL);
+       if (err)
+               goto out2;
 
        /* Create symlink */
        err = ext2fs_symlink(fs, parent, 0, node_name, src);
@@ -1700,7 +1731,7 @@ static int op_symlink(const char *src, const char *dest)
        }
 
        fuse2fs_set_uid(&inode, ctxt->uid);
-       fuse2fs_set_gid(&inode, ctxt->gid);
+       fuse2fs_set_gid(&inode, gid);
        inode.i_generation = ff->next_generation++;
        init_times(&inode);
 
@@ -3240,6 +3271,7 @@ static int op_create(const char *path, mode_t mode, struct fuse_file_info *fp)
        char *node_name, a;
        int filetype;
        struct ext2_inode_large inode;
+       gid_t gid;
        int ret = 0;
 
        FUSE2FS_CHECK_CONTEXT(ff);
@@ -3276,6 +3308,10 @@ static int op_create(const char *path, mode_t mode, struct fuse_file_info *fp)
        if (ret)
                goto out2;
 
+       err = fuse2fs_new_child_gid(ff, parent, &gid, NULL);
+       if (err)
+               goto out2;
+
        *node_name = a;
 
        filetype = ext2_file_type(mode);
@@ -3305,7 +3341,7 @@ static int op_create(const char *path, mode_t mode, struct fuse_file_info *fp)
        inode.i_extra_isize = sizeof(struct ext2_inode_large) -
                EXT2_GOOD_OLD_INODE_SIZE;
        fuse2fs_set_uid(&inode, ctxt->uid);
-       fuse2fs_set_gid(&inode, ctxt->gid);
+       fuse2fs_set_gid(&inode, gid);
        if (ext2fs_has_feature_extents(fs->super)) {
                ext2_extent_handle_t handle;