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Alexey DobriyanLinus Torvalds
Alexey Dobriyan
authored and
Linus Torvalds
committed
proc: fix ->open'less usage due to ->proc_fops flip
Typical PDE creation code looks like: pde = create_proc_entry("foo", 0, NULL); if (pde) pde->proc_fops = &foo_proc_fops; Notice that PDE is first created, only then ->proc_fops is set up to final value. This is a problem because right after creation a) PDE is fully visible in /proc , and b) ->proc_fops are proc_file_operations which do not have ->open callback. So, it's possible to ->read without ->open (see one class of oopses below). The fix is new API called proc_create() which makes sure ->proc_fops are set up before gluing PDE to main tree. Typical new code looks like: pde = proc_create("foo", 0, NULL, &foo_proc_fops); if (!pde) return -ENOMEM; Fix most networking users for a start. In the long run, create_proc_entry() for regular files will go. BUG: unable to handle kernel NULL pointer dereference at virtual address 00000024 printing eip: c1188c1b *pdpt = 000000002929e001 *pde = 0000000000000000 Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC last sysfs file: /sys/block/sda/sda1/dev Modules linked in: foo af_packet ipv6 cpufreq_ondemand loop serio_raw psmouse k8temp hwmon sr_mod cdrom Pid: 24679, comm: cat Not tainted (2.6.24-rc3-mm1 #2) EIP: 0060:[<c1188c1b>] EFLAGS: 00210002 CPU: 0 EIP is at mutex_lock_nested+0x75/0x25d EAX: 000006fe EBX: fffffffb ECX: 00001000 EDX: e9340570 ESI: 00000020 EDI: 00200246 EBP: e9340570 ESP: e8ea1ef8 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 Process cat (pid: 24679, ti=E8EA1000 task=E9340570 task.ti=E8EA1000) Stack: 00000000 c106f7ce e8ee05b4 00000000 00000001 458003d0 f6fb6f20 fffffffb 00000000 c106f7aa 00001000 c106f7ce 08ae9000 f6db53f0 00000020 00200246 00000000 00000002 00000000 00200246 00200246 e8ee05a0 fffffffb e8ee0550 Call Trace: [<c106f7ce>] seq_read+0x24/0x28a [<c106f7aa>] seq_read+0x0/0x28a [<c106f7ce>] seq_read+0x24/0x28a [<c106f7aa>] seq_read+0x0/0x28a [<c10818b8>] proc_reg_read+0x60/0x73 [<c1081858>] proc_reg_read+0x0/0x73 [<c105a34f>] vfs_read+0x6c/0x8b [<c105a6f3>] sys_read+0x3c/0x63 [<c10025f2>] sysenter_past_esp+0x5f/0xa5 [<c10697a7>] destroy_inode+0x24/0x33 ======================= INFO: lockdep is turned off. Code: 75 21 68 e1 1a 19 c1 68 87 00 00 00 68 b8 e8 1f c1 68 25 73 1f c1 e8 84 06 e9 ff e8 52 b8 e7 ff 83 c4 10 9c 5f fa e8 28 89 ea ff <f0> fe 4e 04 79 0a f3 90 80 7e 04 00 7e f8 eb f0 39 76 34 74 33 EIP: [<c1188c1b>] mutex_lock_nested+0x75/0x25d SS:ESP 0068:e8ea1ef8 [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent c6caeb7 commit 2d3a4e3

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4 files changed

+47
-11
lines changed

4 files changed

+47
-11
lines changed

‎fs/proc/generic.c

Lines changed: 36 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -562,7 +562,7 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
562562
return 0;
563563
}
564564

565-
static struct proc_dir_entry *proc_create(struct proc_dir_entry **parent,
565+
static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
566566
const char *name,
567567
mode_t mode,
568568
nlink_t nlink)
@@ -605,7 +605,7 @@ struct proc_dir_entry *proc_symlink(const char *name,
605605
{
606606
struct proc_dir_entry *ent;
607607

608-
ent = proc_create(&parent,name,
608+
ent = __proc_create(&parent, name,
609609
(S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
610610

611611
if (ent) {
@@ -630,7 +630,7 @@ struct proc_dir_entry *proc_mkdir_mode(const char *name, mode_t mode,
630630
{
631631
struct proc_dir_entry *ent;
632632

633-
ent = proc_create(&parent, name, S_IFDIR | mode, 2);
633+
ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
634634
if (ent) {
635635
if (proc_register(parent, ent) < 0) {
636636
kfree(ent);
@@ -664,7 +664,7 @@ struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
664664
nlink = 1;
665665
}
666666

667-
ent = proc_create(&parent,name,mode,nlink);
667+
ent = __proc_create(&parent, name, mode, nlink);
668668
if (ent) {
669669
if (proc_register(parent, ent) < 0) {
670670
kfree(ent);
@@ -674,6 +674,38 @@ struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
674674
return ent;
675675
}
676676

677+
struct proc_dir_entry *proc_create(const char *name, mode_t mode,
678+
struct proc_dir_entry *parent,
679+
const struct file_operations *proc_fops)
680+
{
681+
struct proc_dir_entry *pde;
682+
nlink_t nlink;
683+
684+
if (S_ISDIR(mode)) {
685+
if ((mode & S_IALLUGO) == 0)
686+
mode |= S_IRUGO | S_IXUGO;
687+
nlink = 2;
688+
} else {
689+
if ((mode & S_IFMT) == 0)
690+
mode |= S_IFREG;
691+
if ((mode & S_IALLUGO) == 0)
692+
mode |= S_IRUGO;
693+
nlink = 1;
694+
}
695+
696+
pde = __proc_create(&parent, name, mode, nlink);
697+
if (!pde)
698+
goto out;
699+
pde->proc_fops = proc_fops;
700+
if (proc_register(parent, pde) < 0)
701+
goto out_free;
702+
return pde;
703+
out_free:
704+
kfree(pde);
705+
out:
706+
return NULL;
707+
}
708+
677709
void free_proc_entry(struct proc_dir_entry *de)
678710
{
679711
unsigned int ino = de->low_ino;

‎fs/proc/proc_net.c

Lines changed: 1 addition & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -67,12 +67,7 @@ EXPORT_SYMBOL_GPL(seq_release_net);
6767
struct proc_dir_entry *proc_net_fops_create(struct net *net,
6868
const char *name, mode_t mode, const struct file_operations *fops)
6969
{
70-
struct proc_dir_entry *res;
71-
72-
res = create_proc_entry(name, mode, net->proc_net);
73-
if (res)
74-
res->proc_fops = fops;
75-
return res;
70+
return proc_create(name, mode, net->proc_net, fops);
7671
}
7772
EXPORT_SYMBOL_GPL(proc_net_fops_create);
7873

‎fs/proc/root.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -232,6 +232,7 @@ void pid_ns_release_proc(struct pid_namespace *ns)
232232
EXPORT_SYMBOL(proc_symlink);
233233
EXPORT_SYMBOL(proc_mkdir);
234234
EXPORT_SYMBOL(create_proc_entry);
235+
EXPORT_SYMBOL(proc_create);
235236
EXPORT_SYMBOL(remove_proc_entry);
236237
EXPORT_SYMBOL(proc_root);
237238
EXPORT_SYMBOL(proc_root_fs);

‎include/linux/proc_fs.h

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -126,6 +126,9 @@ void de_put(struct proc_dir_entry *de);
126126

127127
extern struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
128128
struct proc_dir_entry *parent);
129+
struct proc_dir_entry *proc_create(const char *name, mode_t mode,
130+
struct proc_dir_entry *parent,
131+
const struct file_operations *proc_fops);
129132
extern void remove_proc_entry(const char *name, struct proc_dir_entry *parent);
130133

131134
extern struct vfsmount *proc_mnt;
@@ -220,7 +223,12 @@ static inline void proc_flush_task(struct task_struct *task)
220223

221224
static inline struct proc_dir_entry *create_proc_entry(const char *name,
222225
mode_t mode, struct proc_dir_entry *parent) { return NULL; }
223-
226+
static inline struct proc_dir_entry *proc_create(const char *name,
227+
mode_t mode, struct proc_dir_entry *parent,
228+
const struct file_operations *proc_fops)
229+
{
230+
return NULL;
231+
}
224232
#define remove_proc_entry(name, parent) do {} while (0)
225233

226234
static inline struct proc_dir_entry *proc_symlink(const char *name,

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