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authorAlexey Dobriyan <adobriyan@sw.ru>2008-02-08 04:18:37 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-08 09:22:24 -0800
commit2d3a4e3666325a9709cc8ea2e88151394e8f20fc (patch)
treec3e75289de8c824f5e2bb2e97d4b6853d48da3f3 /fs/proc/root.c
parentc6caeb7c4544608e8ae62731334661fc396c7f85 (diff)
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>
Diffstat (limited to 'fs/proc/root.c')
-rw-r--r--fs/proc/root.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 81f99e691f9..ef0fb57fc9e 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -232,6 +232,7 @@ void pid_ns_release_proc(struct pid_namespace *ns)
EXPORT_SYMBOL(proc_symlink);
EXPORT_SYMBOL(proc_mkdir);
EXPORT_SYMBOL(create_proc_entry);
+EXPORT_SYMBOL(proc_create);
EXPORT_SYMBOL(remove_proc_entry);
EXPORT_SYMBOL(proc_root);
EXPORT_SYMBOL(proc_root_fs);