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authorAl Viro <viro@zeniv.linux.org.uk>2009-03-30 07:20:30 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2009-03-31 23:00:26 -0400
commit498052bba55ecaff58db6a1436b0e25bfd75a7ff (patch)
treebd3644ac60737e3733995a203acebd70cfd1b21b /fs/exec.c
parent3e93cd671813e204c258f1e6c797959920cf7772 (diff)
New locking/refcounting for fs_struct
* all changes of current->fs are done under task_lock and write_lock of old fs->lock * refcount is not atomic anymore (same protection) * its decrements are done when removing reference from current; at the same time we decide whether to free it. * put_fs_struct() is gone * new field - ->in_exec. Set by check_unsafe_exec() if we are trying to do execve() and only subthreads share fs_struct. Cleared when finishing exec (success and failure alike). Makes CLONE_FS fail with -EAGAIN if set. * check_unsafe_exec() may fail with -EAGAIN if another execve() from subthread is in progress. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c31
1 files changed, 26 insertions, 5 deletions
diff --git a/fs/exec.c b/fs/exec.c
index c5128fbc916..07a059664b7 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1056,16 +1056,18 @@ EXPORT_SYMBOL(install_exec_creds);
* - the caller must hold current->cred_exec_mutex to protect against
* PTRACE_ATTACH
*/
-void check_unsafe_exec(struct linux_binprm *bprm)
+int check_unsafe_exec(struct linux_binprm *bprm)
{
struct task_struct *p = current, *t;
unsigned long flags;
unsigned n_fs, n_sighand;
+ int res = 0;
bprm->unsafe = tracehook_unsafe_exec(p);
n_fs = 1;
n_sighand = 1;
+ write_lock(&p->fs->lock);
lock_task_sighand(p, &flags);
for (t = next_thread(p); t != p; t = next_thread(t)) {
if (t->fs == p->fs)
@@ -1073,11 +1075,19 @@ void check_unsafe_exec(struct linux_binprm *bprm)
n_sighand++;
}
- if (atomic_read(&p->fs->count) > n_fs ||
- atomic_read(&p->sighand->count) > n_sighand)
+ if (p->fs->users > n_fs ||
+ atomic_read(&p->sighand->count) > n_sighand) {
bprm->unsafe |= LSM_UNSAFE_SHARE;
+ } else {
+ if (p->fs->in_exec)
+ res = -EAGAIN;
+ p->fs->in_exec = 1;
+ }
unlock_task_sighand(p, &flags);
+ write_unlock(&p->fs->lock);
+
+ return res;
}
/*
@@ -1296,12 +1306,15 @@ int do_execve(char * filename,
bprm->cred = prepare_exec_creds();
if (!bprm->cred)
goto out_unlock;
- check_unsafe_exec(bprm);
+
+ retval = check_unsafe_exec(bprm);
+ if (retval)
+ goto out_unlock;
file = open_exec(filename);
retval = PTR_ERR(file);
if (IS_ERR(file))
- goto out_unlock;
+ goto out_unmark;
sched_exec();
@@ -1344,6 +1357,9 @@ int do_execve(char * filename,
goto out;
/* execve succeeded */
+ write_lock(&current->fs->lock);
+ current->fs->in_exec = 0;
+ write_unlock(&current->fs->lock);
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);
acct_update_integrals(current);
@@ -1362,6 +1378,11 @@ out_file:
fput(bprm->file);
}
+out_unmark:
+ write_lock(&current->fs->lock);
+ current->fs->in_exec = 0;
+ write_unlock(&current->fs->lock);
+
out_unlock:
current->in_execve = 0;
mutex_unlock(&current->cred_exec_mutex);