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| author | Amir Goldstein <amir73il@gmail.com> | 2023-10-02 14:21:49 +0300 |
|---|---|---|
| committer | Amir Goldstein <amir73il@gmail.com> | 2023-10-02 17:45:02 +0300 |
| commit | a535116d80339dbfe50b9b81b2f808c69eefbbc3 (patch) | |
| tree | d176b86fe0e19b12774c5564dc787ed2539b81a6 /fs/overlayfs/params.c | |
| parent | c54719c92aa3129f330cce81b88cf34f1627f756 (diff) | |
| download | linux-a535116d80339dbfe50b9b81b2f808c69eefbbc3.tar.gz linux-a535116d80339dbfe50b9b81b2f808c69eefbbc3.tar.bz2 linux-a535116d80339dbfe50b9b81b2f808c69eefbbc3.zip | |
ovl: make use of ->layers safe in rcu pathwalk
ovl_permission() accesses ->layers[...].mnt; we can't have ->layers
freed without an RCU delay on fs shutdown.
Fortunately, kern_unmount_array() that is used to drop those mounts
does include an RCU delay, so freeing is delayed; unfortunately, the
array passed to kern_unmount_array() is formed by mangling ->layers
contents and that happens without any delays.
The ->layers[...].name string entries are used to store the strings to
display in "lowerdir=..." by ovl_show_options(). Those entries are not
accessed in RCU walk.
Move the name strings into a separate array ofs->config.lowerdirs and
reuse the ofs->config.lowerdirs array as the temporary mount array to
pass to kern_unmount_array().
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20231002023711.GP3389589@ZenIV/
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Diffstat (limited to 'fs/overlayfs/params.c')
| -rw-r--r-- | fs/overlayfs/params.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c index b9355bb6d75a..95b751507ac8 100644 --- a/fs/overlayfs/params.c +++ b/fs/overlayfs/params.c @@ -752,12 +752,12 @@ void ovl_free_fs(struct ovl_fs *ofs) if (ofs->upperdir_locked) ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root); - /* Hack! Reuse ofs->layers as a vfsmount array before freeing it */ - mounts = (struct vfsmount **) ofs->layers; + /* Reuse ofs->config.lowerdirs as a vfsmount array before freeing it */ + mounts = (struct vfsmount **) ofs->config.lowerdirs; for (i = 0; i < ofs->numlayer; i++) { iput(ofs->layers[i].trap); + kfree(ofs->config.lowerdirs[i]); mounts[i] = ofs->layers[i].mnt; - kfree(ofs->layers[i].name); } kern_unmount_array(mounts, ofs->numlayer); kfree(ofs->layers); @@ -765,6 +765,7 @@ void ovl_free_fs(struct ovl_fs *ofs) free_anon_bdev(ofs->fs[i].pseudo_dev); kfree(ofs->fs); + kfree(ofs->config.lowerdirs); kfree(ofs->config.upperdir); kfree(ofs->config.workdir); if (ofs->creator_cred) @@ -949,16 +950,16 @@ int ovl_show_options(struct seq_file *m, struct dentry *dentry) struct super_block *sb = dentry->d_sb; struct ovl_fs *ofs = OVL_FS(sb); size_t nr, nr_merged_lower = ofs->numlayer - ofs->numdatalayer; - const struct ovl_layer *data_layers = &ofs->layers[nr_merged_lower]; + char **lowerdatadirs = &ofs->config.lowerdirs[nr_merged_lower]; - /* ofs->layers[0] is the upper layer */ - seq_printf(m, ",lowerdir=%s", ofs->layers[1].name); + /* lowerdirs[] starts from offset 1 */ + seq_printf(m, ",lowerdir=%s", ofs->config.lowerdirs[1]); /* dump regular lower layers */ for (nr = 2; nr < nr_merged_lower; nr++) - seq_printf(m, ":%s", ofs->layers[nr].name); + seq_printf(m, ":%s", ofs->config.lowerdirs[nr]); /* dump data lower layers */ for (nr = 0; nr < ofs->numdatalayer; nr++) - seq_printf(m, "::%s", data_layers[nr].name); + seq_printf(m, "::%s", lowerdatadirs[nr]); if (ofs->config.upperdir) { seq_show_option(m, "upperdir", ofs->config.upperdir); seq_show_option(m, "workdir", ofs->config.workdir); |