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Message-ID: <175182663041.1984706.582232688757289460.stgit@frogsfrogsfrogs>
Date: Sun, 06 Jul 2025 11:31:47 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: [PATCH 4/8] fuse2fs: fix gid inheritance on sgid parent directories
From: Darrick J. Wong <djwong@...nel.org>
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@...r.kernel.org> # v1.43
Fixes: 81cbf1ef4f5dab ("misc: add fuse2fs, a FUSE server for e2fsprogs")
Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
misc/fuse2fs.c | 62 ++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 49 insertions(+), 13 deletions(-)
diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 86fef7765e5e46..0e9576b6ca6aa7 100644
--- 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;
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