[for-linus][PATCH 01/11] tracefs: Revert ccbd54ff54e8 ("tracefs: Restrict tracefs when the kernel is locked down")
From: Steven Rostedt
Date: Sun Oct 13 2019 - 13:44:50 EST
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Running the latest kernel through my "make instances" stress tests, I
triggered the following bug (with KASAN and kmemleak enabled):
mkdir invoked oom-killer:
gfp_mask=0x40cd0(GFP_KERNEL|__GFP_COMP|__GFP_RECLAIMABLE), order=0,
oom_score_adj=0
CPU: 1 PID: 2229 Comm: mkdir Not tainted 5.4.0-rc2-test #325
Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014
Call Trace:
dump_stack+0x64/0x8c
dump_header+0x43/0x3b7
? trace_hardirqs_on+0x48/0x4a
oom_kill_process+0x68/0x2d5
out_of_memory+0x2aa/0x2d0
__alloc_pages_nodemask+0x96d/0xb67
__alloc_pages_node+0x19/0x1e
alloc_slab_page+0x17/0x45
new_slab+0xd0/0x234
___slab_alloc.constprop.86+0x18f/0x336
? alloc_inode+0x2c/0x74
? irq_trace+0x12/0x1e
? tracer_hardirqs_off+0x1d/0xd7
? __slab_alloc.constprop.85+0x21/0x53
__slab_alloc.constprop.85+0x31/0x53
? __slab_alloc.constprop.85+0x31/0x53
? alloc_inode+0x2c/0x74
kmem_cache_alloc+0x50/0x179
? alloc_inode+0x2c/0x74
alloc_inode+0x2c/0x74
new_inode_pseudo+0xf/0x48
new_inode+0x15/0x25
tracefs_get_inode+0x23/0x7c
? lookup_one_len+0x54/0x6c
tracefs_create_file+0x53/0x11d
trace_create_file+0x15/0x33
event_create_dir+0x2a3/0x34b
__trace_add_new_event+0x1c/0x26
event_trace_add_tracer+0x56/0x86
trace_array_create+0x13e/0x1e1
instance_mkdir+0x8/0x17
tracefs_syscall_mkdir+0x39/0x50
? get_dname+0x31/0x31
vfs_mkdir+0x78/0xa3
do_mkdirat+0x71/0xb0
sys_mkdir+0x19/0x1b
do_fast_syscall_32+0xb0/0xed
I bisected this down to the addition of the proxy_ops into tracefs for
lockdown. It appears that the allocation of the proxy_ops and then freeing
it in the destroy_inode callback, is causing havoc with the memory system.
Reading the documentation about destroy_inode and talking with Linus about
this, this is buggy and wrong. When defining the destroy_inode() method, it
is expected that the destroy_inode() will also free the inode, and not just
the extra allocations done in the creation of the inode. The faulty commit
causes a memory leak of the inode data structure when they are deleted.
Instead of allocating the proxy_ops (and then having to free it) the checks
should be done by the open functions themselves, and not hack into the
tracefs directory. First revert the tracefs updates for locked_down and then
later we can add the locked_down checks in the kernel/trace files.
Link: http://lkml.kernel.org/r/20191011135458.7399da44@xxxxxxxxxxxxxxxxxx
Fixes: ccbd54ff54e8 ("tracefs: Restrict tracefs when the kernel is locked down")
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
fs/tracefs/inode.c | 42 +-----------------------------------------
1 file changed, 1 insertion(+), 41 deletions(-)
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 9fc14e38927f..eeeae0475da9 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -20,7 +20,6 @@
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
-#include <linux/security.h>
#define TRACEFS_DEFAULT_MODE 0700
@@ -28,25 +27,6 @@ static struct vfsmount *tracefs_mount;
static int tracefs_mount_count;
static bool tracefs_registered;
-static int default_open_file(struct inode *inode, struct file *filp)
-{
- struct dentry *dentry = filp->f_path.dentry;
- struct file_operations *real_fops;
- int ret;
-
- if (!dentry)
- return -EINVAL;
-
- ret = security_locked_down(LOCKDOWN_TRACEFS);
- if (ret)
- return ret;
-
- real_fops = dentry->d_fsdata;
- if (!real_fops->open)
- return 0;
- return real_fops->open(inode, filp);
-}
-
static ssize_t default_read_file(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
@@ -241,12 +221,6 @@ static int tracefs_apply_options(struct super_block *sb)
return 0;
}
-static void tracefs_destroy_inode(struct inode *inode)
-{
- if (S_ISREG(inode->i_mode))
- kfree(inode->i_fop);
-}
-
static int tracefs_remount(struct super_block *sb, int *flags, char *data)
{
int err;
@@ -283,7 +257,6 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root)
static const struct super_operations tracefs_super_operations = {
.statfs = simple_statfs,
.remount_fs = tracefs_remount,
- .destroy_inode = tracefs_destroy_inode,
.show_options = tracefs_show_options,
};
@@ -414,7 +387,6 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
{
- struct file_operations *proxy_fops;
struct dentry *dentry;
struct inode *inode;
@@ -430,20 +402,8 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
if (unlikely(!inode))
return failed_creating(dentry);
- proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL);
- if (unlikely(!proxy_fops)) {
- iput(inode);
- return failed_creating(dentry);
- }
-
- if (!fops)
- fops = &tracefs_file_operations;
-
- dentry->d_fsdata = (void *)fops;
- memcpy(proxy_fops, fops, sizeof(*proxy_fops));
- proxy_fops->open = default_open_file;
inode->i_mode = mode;
- inode->i_fop = proxy_fops;
+ inode->i_fop = fops ? fops : &tracefs_file_operations;
inode->i_private = data;
d_instantiate(dentry, inode);
fsnotify_create(dentry->d_parent->d_inode, dentry);
--
2.23.0