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authorAlexey Dobriyan <adobriyan@sw.ru>2007-07-15 23:39:00 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:39 -0700
commit786d7e1612f0b0adb6046f19b906609e4fe8b1ba (patch)
tree9d5f1623c19c9d3f84606ea160d57cd3c8c97ea9 /include
parent5568b0e8028d966ddb16f0be44a9df1fcbd1dc8d (diff)
Fix rmmod/read/write races in /proc entries
Fix following races: =========================================== 1. Write via ->write_proc sleeps in copy_from_user(). Module disappears meanwhile. Or, more generically, system call done on /proc file, method supplied by module is called, module dissapeares meanwhile. pde = create_proc_entry() if (!pde) return -ENOMEM; pde->write_proc = ... open write copy_from_user pde = create_proc_entry(); if (!pde) { remove_proc_entry(); return -ENOMEM; /* module unloaded */ } *boom* ========================================== 2. bogo-revoke aka proc_kill_inodes() remove_proc_entry vfs_read proc_kill_inodes [check ->f_op validness] [check ->f_op->read validness] [verify_area, security permissions checks] ->f_op = NULL; if (file->f_op->read) /* ->f_op dereference, boom */ NOTE, NOTE, NOTE: file_operations are proxied for regular files only. Let's see how this scheme behaves, then extend if needed for directories. Directories creators in /proc only set ->owner for them, so proxying for directories may be unneeded. NOTE, NOTE, NOTE: methods being proxied are ->llseek, ->read, ->write, ->poll, ->unlocked_ioctl, ->ioctl, ->compat_ioctl, ->open, ->release. If your in-tree module uses something else, yell on me. Full audit pending. [akpm@linux-foundation.org: build fix] Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/proc_fs.h13
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 3469f96bc8b..28e3664fdf1 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -7,6 +7,8 @@
#include <linux/magic.h>
#include <asm/atomic.h>
+struct completion;
+
/*
* The proc filesystem constants/structures
*/
@@ -56,6 +58,14 @@ struct proc_dir_entry {
gid_t gid;
loff_t size;
const struct inode_operations *proc_iops;
+ /*
+ * NULL ->proc_fops means "PDE is going away RSN" or
+ * "PDE is just created". In either case, e.g. ->read_proc won't be
+ * called because it's too late or too early, respectively.
+ *
+ * If you're allocating ->proc_fops dynamically, save a pointer
+ * somewhere.
+ */
const struct file_operations *proc_fops;
get_info_t *get_info;
struct module *owner;
@@ -66,6 +76,9 @@ struct proc_dir_entry {
atomic_t count; /* use count */
int deleted; /* delete flag */
void *set;
+ int pde_users; /* number of callers into module in progress */
+ spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
+ struct completion *pde_unload_completion;
};
struct kcore_list {