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| author | Oleg Nesterov <oleg@redhat.com> | 2009-04-24 01:02:45 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-24 16:39:45 +0200 |
| commit | 437f7fdb607f32b737e4da9f14bebcfdac2c90c3 (patch) | |
| tree | 2064149ad4406774bd3b1ade60782980206f2e82 | |
| parent | do_execve() must not clear fs->in_exec if it was set by another thread (diff) | |
| download | linux-437f7fdb607f32b737e4da9f14bebcfdac2c90c3.tar.xz linux-437f7fdb607f32b737e4da9f14bebcfdac2c90c3.zip | |
check_unsafe_exec: s/lock_task_sighand/rcu_read_lock/
write_lock(¤t->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.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/fs/exec.c b/fs/exec.c index a2e6989dbc3a..a3a8ce83940f 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; |