Messages in this thread Patch in this message | | | Date | Sun, 15 Nov 2009 01:51:53 -0500 | From | Mathieu Desnoyers <> | Subject | [PATCH] Debugfs: fix create mutex racy fops and private data |
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Setting fops and private data outside of the mutex at debugfs file creation introduces a race where the files can be opened with the wrong file operations and private data. It is easy to trigger with a process waiting on file creation notification.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> CC: Greg Kroah-Hartman <greg@kroah.com> --- fs/debugfs/inode.c | 55 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 32 insertions(+), 23 deletions(-)
Index: linux-2.6-lttng/fs/debugfs/inode.c =================================================================== --- linux-2.6-lttng.orig/fs/debugfs/inode.c 2009-11-15 01:22:59.000000000 -0500 +++ linux-2.6-lttng/fs/debugfs/inode.c 2009-11-15 01:42:46.000000000 -0500 @@ -32,7 +32,9 @@ static struct vfsmount *debugfs_mount; static int debugfs_mount_count; static bool debugfs_registered; -static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev) +static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev, + void *data, const struct file_operations *fops) + { struct inode *inode = new_inode(sb); @@ -44,14 +46,18 @@ static struct inode *debugfs_get_inode(s init_special_inode(inode, mode, dev); break; case S_IFREG: - inode->i_fop = &debugfs_file_operations; + inode->i_fop = fops ? fops : &debugfs_file_operations; + inode->i_private = data; break; case S_IFLNK: inode->i_op = &debugfs_link_operations; + inode->i_fop = fops; + inode->i_private = data; break; case S_IFDIR: inode->i_op = &simple_dir_inode_operations; - inode->i_fop = &simple_dir_operations; + inode->i_fop = fops ? fops : &simple_dir_operations; + inode->i_private = data; /* directory inodes start off with i_nlink == 2 * (for "." entry) */ @@ -64,7 +70,8 @@ static struct inode *debugfs_get_inode(s /* SMP-safe */ static int debugfs_mknod(struct inode *dir, struct dentry *dentry, - int mode, dev_t dev) + int mode, dev_t dev, void *data, + const struct file_operations *fops) { struct inode *inode; int error = -EPERM; @@ -72,7 +79,7 @@ static int debugfs_mknod(struct inode *d if (dentry->d_inode) return -EEXIST; - inode = debugfs_get_inode(dir->i_sb, mode, dev); + inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops); if (inode) { d_instantiate(dentry, inode); dget(dentry); @@ -81,12 +88,13 @@ static int debugfs_mknod(struct inode *d return error; } -static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) +static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode, + void *data, const struct file_operations *fops) { int res; mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR; - res = debugfs_mknod(dir, dentry, mode, 0); + res = debugfs_mknod(dir, dentry, mode, 0, data, fops); if (!res) { inc_nlink(dir); fsnotify_mkdir(dir, dentry); @@ -94,18 +102,20 @@ static int debugfs_mkdir(struct inode *d return res; } -static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode) +static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode, + void *data, const struct file_operations *fops) { mode = (mode & S_IALLUGO) | S_IFLNK; - return debugfs_mknod(dir, dentry, mode, 0); + return debugfs_mknod(dir, dentry, mode, 0, data, fops); } -static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode) +static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode, + void *data, const struct file_operations *fops) { int res; mode = (mode & S_IALLUGO) | S_IFREG; - res = debugfs_mknod(dir, dentry, mode, 0); + res = debugfs_mknod(dir, dentry, mode, 0, data, fops); if (!res) fsnotify_create(dir, dentry); return res; @@ -139,7 +149,9 @@ static struct file_system_type debug_fs_ static int debugfs_create_by_name(const char *name, mode_t mode, struct dentry *parent, - struct dentry **dentry) + struct dentry **dentry, + void *data, + const struct file_operations *fops) { int error = 0; @@ -164,13 +176,16 @@ static int debugfs_create_by_name(const if (!IS_ERR(*dentry)) { switch (mode & S_IFMT) { case S_IFDIR: - error = debugfs_mkdir(parent->d_inode, *dentry, mode); + error = debugfs_mkdir(parent->d_inode, *dentry, mode, + data, fops); break; case S_IFLNK: - error = debugfs_link(parent->d_inode, *dentry, mode); + error = debugfs_link(parent->d_inode, *dentry, mode, + data, fops); break; default: - error = debugfs_create(parent->d_inode, *dentry, mode); + error = debugfs_create(parent->d_inode, *dentry, mode, + data, fops); break; } dput(*dentry); @@ -221,19 +236,13 @@ struct dentry *debugfs_create_file(const if (error) goto exit; - error = debugfs_create_by_name(name, mode, parent, &dentry); + error = debugfs_create_by_name(name, mode, parent, &dentry, + data, fops); if (error) { dentry = NULL; simple_release_fs(&debugfs_mount, &debugfs_mount_count); goto exit; } - - if (dentry->d_inode) { - if (data) - dentry->d_inode->i_private = data; - if (fops) - dentry->d_inode->i_fop = fops; - } exit: return dentry; } -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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