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ovl: do not encode lower fh with upper sb_writers held

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When lower fs is a nested overlayfs, calling encode_fh() on a lower
directory dentry may trigger copy up and take sb_writers on the upper fs
of the lower nested overlayfs.

The lower nested overlayfs may have the same upper fs as this overlayfs,
so nested sb_writers lock is illegal.

Move all the callers that encode lower fh to before ovl_want_write().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
This commit is contained in:
Amir Goldstein 2023-08-16 16:47:59 +03:00
parent c63e56a4a6
commit 5b02bfc1e7
5 changed files with 104 additions and 43 deletions
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53
fs/overlayfs/copy_up.c
View File

@ -434,29 +434,29 @@ out_err:
return ERR_PTR(err);
}
int ovl_set_origin(struct ovl_fs *ofs, struct dentry *lower,
struct dentry *upper)
struct ovl_fh *ovl_get_origin_fh(struct ovl_fs *ofs, struct dentry *origin)
{
const struct ovl_fh *fh = NULL;
int err;
/*
* When lower layer doesn't support export operations store a 'null' fh,
* so we can use the overlay.origin xattr to distignuish between a copy
* up and a pure upper inode.
*/
if (ovl_can_decode_fh(lower->d_sb)) {
fh = ovl_encode_real_fh(ofs, lower, false);
if (IS_ERR(fh))
return PTR_ERR(fh);
}
if (!ovl_can_decode_fh(origin->d_sb))
return NULL;
return ovl_encode_real_fh(ofs, origin, false);
}
int ovl_set_origin_fh(struct ovl_fs *ofs, const struct ovl_fh *fh,
struct dentry *upper)
{
int err;
/*
* Do not fail when upper doesn't support xattrs.
*/
err = ovl_check_setxattr(ofs, upper, OVL_XATTR_ORIGIN, fh->buf,
fh ? fh->fb.len : 0, 0);
kfree(fh);
/* Ignore -EPERM from setting "user.*" on symlink/special */
return err == -EPERM ? 0 : err;
@ -484,7 +484,7 @@ static int ovl_set_upper_fh(struct ovl_fs *ofs, struct dentry *upper,
*
* Caller must hold i_mutex on indexdir.
*/
static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
static int ovl_create_index(struct dentry *dentry, const struct ovl_fh *fh,
struct dentry *upper)
{
struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
@ -510,7 +510,7 @@ static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
if (WARN_ON(ovl_test_flag(OVL_INDEX, d_inode(dentry))))
return -EIO;
err = ovl_get_index_name(ofs, origin, &name);
err = ovl_get_index_name_fh(fh, &name);
if (err)
return err;
@ -549,6 +549,7 @@ struct ovl_copy_up_ctx {
struct dentry *destdir;
struct qstr destname;
struct dentry *workdir;
const struct ovl_fh *origin_fh;
bool origin;
bool indexed;
bool metacopy;
@ -649,7 +650,7 @@ static int ovl_copy_up_metadata(struct ovl_copy_up_ctx *c, struct dentry *temp)
* hard link.
*/
if (c->origin) {
err = ovl_set_origin(ofs, c->lowerpath.dentry, temp);
err = ovl_set_origin_fh(ofs, c->origin_fh, temp);
if (err)
return err;
}
@ -772,7 +773,7 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
goto cleanup;
if (S_ISDIR(c->stat.mode) && c->indexed) {
err = ovl_create_index(c->dentry, c->lowerpath.dentry, temp);
err = ovl_create_index(c->dentry, c->origin_fh, temp);
if (err)
goto cleanup;
}
@ -890,6 +891,8 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
{
int err;
struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb);
struct dentry *origin = c->lowerpath.dentry;
struct ovl_fh *fh = NULL;
bool to_index = false;
/*
@ -906,17 +909,25 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
to_index = true;
}
if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || to_index)
if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || to_index) {
fh = ovl_get_origin_fh(ofs, origin);
if (IS_ERR(fh))
return PTR_ERR(fh);
/* origin_fh may be NULL */
c->origin_fh = fh;
c->origin = true;
}
if (to_index) {
c->destdir = ovl_indexdir(c->dentry->d_sb);
err = ovl_get_index_name(ofs, c->lowerpath.dentry, &c->destname);
err = ovl_get_index_name(ofs, origin, &c->destname);
if (err)
return err;
goto out_free_fh;
} else if (WARN_ON(!c->parent)) {
/* Disconnected dentry must be copied up to index dir */
return -EIO;
err = -EIO;
goto out_free_fh;
} else {
/*
* Mark parent "impure" because it may now contain non-pure
@ -926,7 +937,7 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
err = ovl_set_impure(c->parent, c->destdir);
ovl_end_write(c->dentry);
if (err)
return err;
goto out_free_fh;
}
/* Should we copyup with O_TMPFILE or with workdir? */
@ -960,6 +971,8 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
out:
if (to_index)
kfree(c->destname.name);
out_free_fh:
kfree(fh);
return err;
}

37
fs/overlayfs/namei.c
View File

@ -507,6 +507,19 @@ static int ovl_verify_fh(struct ovl_fs *ofs, struct dentry *dentry,
return err;
}
int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, const struct ovl_fh *fh,
bool is_upper, bool set)
{
int err;
err = ovl_verify_fh(ofs, dentry, ox, fh);
if (set && err == -ENODATA)
err = ovl_setxattr(ofs, dentry, ox, fh->buf, fh->fb.len);
return err;
}
/*
* Verify that @real dentry matches the file handle stored in xattr @name.
*
@ -515,9 +528,9 @@ static int ovl_verify_fh(struct ovl_fs *ofs, struct dentry *dentry,
*
* Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
*/
int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, struct dentry *real, bool is_upper,
bool set)
int ovl_verify_origin_xattr(struct ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, struct dentry *real,
bool is_upper, bool set)
{
struct inode *inode;
struct ovl_fh *fh;
@ -530,9 +543,7 @@ int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry,
goto fail;
}
err = ovl_verify_fh(ofs, dentry, ox, fh);
if (set && err == -ENODATA)
err = ovl_setxattr(ofs, dentry, ox, fh->buf, fh->fb.len);
err = ovl_verify_set_fh(ofs, dentry, ox, fh, is_upper, set);
if (err)
goto fail;
@ -548,6 +559,7 @@ fail:
goto out;
}
/* Get upper dentry from index */
struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index,
bool connected)
@ -684,7 +696,7 @@ orphan:
goto out;
}
static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name)
int ovl_get_index_name_fh(const struct ovl_fh *fh, struct qstr *name)
{
char *n, *s;
@ -873,20 +885,27 @@ int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
static int ovl_fix_origin(struct ovl_fs *ofs, struct dentry *dentry,
struct dentry *lower, struct dentry *upper)
{
const struct ovl_fh *fh;
int err;
if (ovl_check_origin_xattr(ofs, upper))
return 0;
fh = ovl_get_origin_fh(ofs, lower);
if (IS_ERR(fh))
return PTR_ERR(fh);
err = ovl_want_write(dentry);
if (err)
return err;
goto out;
err = ovl_set_origin(ofs, lower, upper);
err = ovl_set_origin_fh(ofs, fh, upper);
if (!err)
err = ovl_set_impure(dentry->d_parent, upper->d_parent);
ovl_drop_write(dentry);
out:
kfree(fh);
return err;
}

26
fs/overlayfs/overlayfs.h
View File

@ -628,11 +628,15 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
struct dentry *upperdentry, struct ovl_path **stackp);
int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, struct dentry *real, bool is_upper,
bool set);
enum ovl_xattr ox, const struct ovl_fh *fh,
bool is_upper, bool set);
int ovl_verify_origin_xattr(struct ovl_fs *ofs, struct dentry *dentry,
enum ovl_xattr ox, struct dentry *real,
bool is_upper, bool set);
struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index,
bool connected);
int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index);
int ovl_get_index_name_fh(const struct ovl_fh *fh, struct qstr *name);
int ovl_get_index_name(struct ovl_fs *ofs, struct dentry *origin,
struct qstr *name);
struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh);
@ -644,17 +648,24 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags);
bool ovl_lower_positive(struct dentry *dentry);
static inline int ovl_verify_origin_fh(struct ovl_fs *ofs, struct dentry *upper,
const struct ovl_fh *fh, bool set)
{
return ovl_verify_set_fh(ofs, upper, OVL_XATTR_ORIGIN, fh, false, set);
}
static inline int ovl_verify_origin(struct ovl_fs *ofs, struct dentry *upper,
struct dentry *origin, bool set)
{
return ovl_verify_set_fh(ofs, upper, OVL_XATTR_ORIGIN, origin,
false, set);
return ovl_verify_origin_xattr(ofs, upper, OVL_XATTR_ORIGIN, origin,
false, set);
}
static inline int ovl_verify_upper(struct ovl_fs *ofs, struct dentry *index,
struct dentry *upper, bool set)
{
return ovl_verify_set_fh(ofs, index, OVL_XATTR_UPPER, upper, true, set);
return ovl_verify_origin_xattr(ofs, index, OVL_XATTR_UPPER, upper,
true, set);
}
/* readdir.c */
@ -819,8 +830,9 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *path, struct dentr
int ovl_set_attr(struct ovl_fs *ofs, struct dentry *upper, struct kstat *stat);
struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real,
bool is_upper);
int ovl_set_origin(struct ovl_fs *ofs, struct dentry *lower,
struct dentry *upper);
struct ovl_fh *ovl_get_origin_fh(struct ovl_fs *ofs, struct dentry *origin);
int ovl_set_origin_fh(struct ovl_fs *ofs, const struct ovl_fh *fh,
struct dentry *upper);
/* export.c */
extern const struct export_operations ovl_export_operations;

20
fs/overlayfs/super.c
View File

@ -887,15 +887,20 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
{
struct vfsmount *mnt = ovl_upper_mnt(ofs);
struct dentry *indexdir;
struct dentry *origin = ovl_lowerstack(oe)->dentry;
const struct ovl_fh *fh;
int err;
fh = ovl_get_origin_fh(ofs, origin);
if (IS_ERR(fh))
return PTR_ERR(fh);
err = mnt_want_write(mnt);
if (err)
return err;
goto out_free_fh;
/* Verify lower root is upper root origin */
err = ovl_verify_origin(ofs, upperpath->dentry,
ovl_lowerstack(oe)->dentry, true);
err = ovl_verify_origin_fh(ofs, upperpath->dentry, fh, true);
if (err) {
pr_err("failed to verify upper root origin\n");
goto out;
@ -927,9 +932,10 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
* directory entries.
*/
if (ovl_check_origin_xattr(ofs, ofs->indexdir)) {
err = ovl_verify_set_fh(ofs, ofs->indexdir,
OVL_XATTR_ORIGIN,
upperpath->dentry, true, false);
err = ovl_verify_origin_xattr(ofs, ofs->indexdir,
OVL_XATTR_ORIGIN,
upperpath->dentry, true,
false);
if (err)
pr_err("failed to verify index dir 'origin' xattr\n");
}
@ -947,6 +953,8 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
out:
mnt_drop_write(mnt);
out_free_fh:
kfree(fh);
return err;
}

11
fs/overlayfs/util.c
View File

@ -1013,12 +1013,18 @@ static void ovl_cleanup_index(struct dentry *dentry)
struct dentry *index = NULL;
struct inode *inode;
struct qstr name = { };
bool got_write = false;
int err;
err = ovl_get_index_name(ofs, lowerdentry, &name);
if (err)
goto fail;
err = ovl_want_write(dentry);
if (err)
goto fail;
got_write = true;
inode = d_inode(upperdentry);
if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
pr_warn_ratelimited("cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
@ -1056,6 +1062,8 @@ static void ovl_cleanup_index(struct dentry *dentry)
goto fail;
out:
if (got_write)
ovl_drop_write(dentry);
kfree(name.name);
dput(index);
return;
@ -1135,6 +1143,8 @@ void ovl_nlink_end(struct dentry *dentry)
{
struct inode *inode = d_inode(dentry);
ovl_drop_write(dentry);
if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
const struct cred *old_cred;
@ -1143,7 +1153,6 @@ void ovl_nlink_end(struct dentry *dentry)
revert_creds(old_cred);
}
ovl_drop_write(dentry);
ovl_inode_unlock(inode);
}