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authorOleg Nesterov <oleg@redhat.com>2009-04-24 01:02:45 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-24 07:39:45 -0700
commit437f7fdb607f32b737e4da9f14bebcfdac2c90c3 (patch)
tree2064149ad4406774bd3b1ade60782980206f2e82
parent8c652f96d3852b97a49c331cd0bb02d22f3cb31b (diff)
check_unsafe_exec: s/lock_task_sighand/rcu_read_lock/
write_lock(&current->fs->lock) guarantees we can't wrongly miss LSM_UNSAFE_SHARE, this is what we care about. Use rcu_read_lock() instead of ->siglock to iterate over the sub-threads. We must see all CLONE_THREAD|CLONE_FS threads which didn't pass exit_fs(), it takes fs->lock too. With or without this patch we can miss the freshly cloned thread and set LSM_UNSAFE_SHARE, we don't care. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Roland McGrath <roland@redhat.com> [ Fixed lock/unlock typo - Hugh ] Acked-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/exec.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/fs/exec.c b/fs/exec.c
index a2e6989dbc3..a3a8ce83940 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1060,7 +1060,6 @@ EXPORT_SYMBOL(install_exec_creds);
int check_unsafe_exec(struct linux_binprm *bprm)
{
struct task_struct *p = current, *t;
- unsigned long flags;
unsigned n_fs;
int res = 0;
@@ -1068,11 +1067,12 @@ int check_unsafe_exec(struct linux_binprm *bprm)
n_fs = 1;
write_lock(&p->fs->lock);
- lock_task_sighand(p, &flags);
+ rcu_read_lock();
for (t = next_thread(p); t != p; t = next_thread(t)) {
if (t->fs == p->fs)
n_fs++;
}
+ rcu_read_unlock();
if (p->fs->users > n_fs) {
bprm->unsafe |= LSM_UNSAFE_SHARE;
@@ -1083,8 +1083,6 @@ int check_unsafe_exec(struct linux_binprm *bprm)
res = 1;
}
}
-
- unlock_task_sighand(p, &flags);
write_unlock(&p->fs->lock);
return res;