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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2019-10-11 13:54:58 -0400
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-10-12 20:36:50 -0400
commit3ed270b129a45c7c502c819a4286b464a52dac61 (patch)
tree5173c8b9a382ed33cb604fb0cd176c17efb5cc47
parentda0c9ea146cbe92b832f1b0f694840ea8eb33cce (diff)
downloadlinux-sh-3ed270b129a45c7c502c819a4286b464a52dac61.tar.gz
tracefs: Revert ccbd54ff54e8 ("tracefs: Restrict tracefs when the kernel is locked down")
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@gandalf.local.home Fixes: ccbd54ff54e8 ("tracefs: Restrict tracefs when the kernel is locked down") Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-rw-r--r--fs/tracefs/inode.c42
1 files changed, 1 insertions, 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);