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authorMing Lei <ming.lei@canonical.com>2013-04-04 22:22:37 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-04-05 15:35:52 -0700
commitbb2b0051d7b0772ea9d0b4be900c2d965093f5d7 (patch)
treeea77b283a68b2b2a5cbcf29706d8c2d6361d18e6
parentbcfb87fb75fa3a9b96c8a73d19166897d167fe3f (diff)
downloadlinaro-lsk-bb2b0051d7b0772ea9d0b4be900c2d965093f5d7.tar.gz
sysfs: check if one entry has been removed before freeing
It might be a kernel disaster if one sysfs entry is freed but still referenced by sysfs tree. Recently Dave and Sasha reported one use-after-free problem on sysfs entry, and the problem has been troubleshooted with help of debug message added in this patch. Given sysfs_get_dirent/sysfs_put are exported APIs, even inside sysfs they are called in many contexts(kobject/attribe add/delete, inode init/drop, dentry lookup/release, readdir, ...), it is healthful to check the removed flag before freeing one entry and dump message if it is freeing without being removed first. Cc: Dave Jones <davej@redhat.com> Cc: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/sysfs/dir.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 1bf016b5e88..e8e0e71b29d 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -268,6 +268,10 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
*/
parent_sd = sd->s_parent;
+ WARN(!(sd->s_flags & SYSFS_FLAG_REMOVED),
+ "sysfs: free using entry: %s/%s\n",
+ parent_sd ? parent_sd->s_name : "", sd->s_name);
+
if (sysfs_type(sd) == SYSFS_KOBJ_LINK)
sysfs_put(sd->s_symlink.target_sd);
if (sysfs_type(sd) & SYSFS_COPY_NAME)
@@ -386,7 +390,7 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
sd->s_name = name;
sd->s_mode = mode;
- sd->s_flags = type;
+ sd->s_flags = type | SYSFS_FLAG_REMOVED;
return sd;
@@ -466,6 +470,9 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
}
+ /* Mark the entry added into directory tree */
+ sd->s_flags &= ~SYSFS_FLAG_REMOVED;
+
return 0;
}