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proc: proc_pid_ns takes super_block as an argument

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syzbot found that

  touch /proc/testfile

causes NULL pointer dereference at tomoyo_get_local_path()
because inode of the dentry is NULL.

Before c59f415a7c, Tomoyo received pid_ns from proc's s_fs_info
directly. Since proc_pid_ns() can only work with inode, using it in
the tomoyo_get_local_path() was wrong.

To avoid creating more functions for getting proc_ns, change the
argument type of the proc_pid_ns() function. Then, Tomoyo can use
the existing super_block to get pid_ns.

Link: https://lkml.kernel.org/r/0000000000002f0c7505a5b0e04c@google.com
Link: https://lkml.kernel.org/r/20200518180738.2939611-1-gladkov.alexey@gmail.com
Reported-by: syzbot+c1af344512918c61362c@syzkaller.appspotmail.com
Fixes: c59f415a7c ("Use proc_pid_ns() to get pid_namespace from the proc superblock")
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Alexey Gladkov
2020-05-18 20:07:38 +02:00
committed by Eric W. Biederman
parent 2dd8083f6d
commit 9d78edeaec
9 changed files with 15 additions and 15 deletions
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2
security/tomoyo/realpath.c
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@@ -162,7 +162,7 @@ static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
char *ep;
const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry));
struct pid_namespace *proc_pidns = proc_pid_ns(sb);
if (*ep == '/' && pid && pid ==
task_tgid_nr_ns(current, proc_pidns)) {