[Devel] [PATCH RHEL8 COMMIT] fs/ovelayfs: Fix crash on overlayfs mount
Konstantin Khorenko
khorenko at virtuozzo.com
Wed Jan 27 16:46:48 MSK 2021
The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.4
------>
commit 4267859a056ae596d339de2b508ca56531000ca3
Author: Andrey Ryabinin <aryabinin at virtuozzo.com>
Date: Wed Jan 27 16:46:47 2021 +0300
fs/ovelayfs: Fix crash on overlayfs mount
Kdump kernel fails to load because of crash on mount of overlayfs:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000060
....
Call Trace:
seq_path+0x64/0xb0
print_paths_option+0x79/0xa0
ovl_show_options+0x3a/0x320
show_mountinfo+0x1ee/0x290
seq_read+0x2f8/0x400
vfs_read+0x9d/0x150
ksys_read+0x4f/0xb0
do_syscall_64+0x5b/0x1a0
This is cause by OOB access of ofs->lowerpaths.
We transfer to print_paths_option() ofs->numlayer as size of ->lowerpaths
array, but it's not.
The correct number of lowerpaths elements is ->numlower in 'struct ovl_entry'.
So move lowerpaths there and use oe->numlower as array size.
Fixes: 17fc61697f73 ("overlayfs: add dynamic path resolving in mount options")
Fixes: 2191d729083d ("overlayfs: add mnt_id paths options")
https://jira.sw.ru/browse/PSBM-123508
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Reviewed-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
---
fs/overlayfs/ovl_entry.h | 2 +-
fs/overlayfs/super.c | 37 ++++++++++++++++++++-----------------
2 files changed, 21 insertions(+), 18 deletions(-)
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index ea1906448ec5..2315089a0211 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -54,7 +54,6 @@ struct ovl_fs {
unsigned int numlayer;
/* Number of unique fs among layers including upper fs */
unsigned int numfs;
- struct path *lowerpaths;
const struct ovl_layer *layers;
struct ovl_sb *fs;
/* workbasepath is the path at workdir= mount option */
@@ -98,6 +97,7 @@ struct ovl_entry {
struct rcu_head rcu;
};
unsigned numlower;
+ struct path *lowerpaths;
struct ovl_path lowerstack[];
};
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 3755f280036f..fb419617564c 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -70,8 +70,12 @@ static void ovl_entry_stack_free(struct ovl_entry *oe)
{
unsigned int i;
- for (i = 0; i < oe->numlower; i++)
+ for (i = 0; i < oe->numlower; i++) {
dput(oe->lowerstack[i].dentry);
+ if (oe->lowerpaths)
+ path_put(&oe->lowerpaths[i]);
+ }
+ kfree(oe->lowerpaths);
}
static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
@@ -241,11 +245,6 @@ static void ovl_free_fs(struct ovl_fs *ofs)
ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
mntput(ofs->upper_mnt);
path_put(&ofs->upperpath);
- if (ofs->lowerpaths) {
- for (i = 0; i < ofs->numlayer; i++)
- path_put(&ofs->lowerpaths[i]);
- kfree(ofs->lowerpaths);
- }
for (i = 1; i < ofs->numlayer; i++) {
iput(ofs->layers[i].trap);
mntput(ofs->layers[i].mnt);
@@ -359,9 +358,10 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
struct super_block *sb = dentry->d_sb;
struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_entry *oe = OVL_E(dentry);
if (ovl_dyn_path_opts) {
- print_paths_option(m, "lowerdir", ofs->lowerpaths, ofs->numlayer);
+ print_paths_option(m, "lowerdir", oe->lowerpaths, oe->numlower);
if (ofs->config.upperdir) {
print_path_option(m, "upperdir", &ofs->upperpath);
print_path_option(m, "workdir", &ofs->workbasepath);
@@ -375,7 +375,7 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
}
if (ovl_mnt_id_path_opts) {
- print_mnt_ids_option(m, "lowerdir_mnt_id", ofs->lowerpaths, ofs->numlayer);
+ print_mnt_ids_option(m, "lowerdir_mnt_id", oe->lowerpaths, oe->numlower);
/*
* We don't need to show mnt_id for workdir because it
* on the same mount as upperdir.
@@ -1626,6 +1626,7 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
int err;
char *lowertmp, *lower;
unsigned int stacklen, numlower = 0, i;
+ struct path *stack = NULL;
struct ovl_entry *oe;
err = -ENOMEM;
@@ -1649,14 +1650,14 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
}
err = -ENOMEM;
- ofs->lowerpaths = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
- if (!ofs->lowerpaths)
+ stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
+ if (!stack)
goto out_err;
err = -EINVAL;
lower = lowertmp;
for (numlower = 0; numlower < stacklen; numlower++) {
- err = ovl_lower_dir(lower, &ofs->lowerpaths[numlower], ofs,
+ err = ovl_lower_dir(lower, &stack[numlower], ofs,
&sb->s_stack_depth);
if (err)
goto out_err;
@@ -1671,7 +1672,7 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
goto out_err;
}
- err = ovl_get_layers(sb, ofs, ofs->lowerpaths, numlower);
+ err = ovl_get_layers(sb, ofs, stack, numlower);
if (err)
goto out_err;
@@ -1681,9 +1682,10 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
goto out_err;
for (i = 0; i < numlower; i++) {
- oe->lowerstack[i].dentry = dget(ofs->lowerpaths[i].dentry);
+ oe->lowerstack[i].dentry = dget(stack[i].dentry);
oe->lowerstack[i].layer = &ofs->layers[i+1];
}
+ oe->lowerpaths = stack;
out:
kfree(lowertmp);
@@ -1691,10 +1693,11 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
return oe;
out_err:
- for (i = 0; i < numlower; i++)
- path_put_init(&ofs->lowerpaths[i]);
- kfree(ofs->lowerpaths);
- ofs->lowerpaths = NULL;
+ if (stack) {
+ for (i = 0; i < numlower; i++)
+ path_put(&stack[i]);
+ kfree(stack);
+ }
oe = ERR_PTR(err);
goto out;
}
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