This changes perf_event_set_clock to use the new exec_update_mutex
instead of cred_guard_mutex.
This should be safe, as the credentials are only used for reading.
Signed-off-by: Bernd Edlinger <bernd.edlinger(a)hotmail.de>
---
kernel/events/core.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e453589..71cba8c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1249,7 +1249,7 @@ static void put_ctx(struct perf_event_context *ctx)
* function.
*
* Lock order:
- * cred_guard_mutex
+ * exec_update_mutex
* task_struct::perf_event_mutex
* perf_event_context::mutex
* perf_event::child_mutex;
@@ -11263,14 +11263,14 @@ static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
}
if (task) {
- err = mutex_lock_interruptible(&task->signal->cred_guard_mutex);
+ err = mutex_lock_interruptible(&task->signal->exec_update_mutex);
if (err)
goto err_task;
/*
* Reuse ptrace permission checks for now.
*
- * We must hold cred_guard_mutex across this and any potential
+ * We must hold exec_update_mutex across this and any potential
* perf_install_in_context() call for this new event to
* serialize against exec() altering our credentials (and the
* perf_event_exit_task() that could imply).
@@ -11559,7 +11559,7 @@ static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
mutex_unlock(&ctx->mutex);
if (task) {
- mutex_unlock(&task->signal->cred_guard_mutex);
+ mutex_unlock(&task->signal->exec_update_mutex);
put_task_struct(task);
}
@@ -11595,7 +11595,7 @@ static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
free_event(event);
err_cred:
if (task)
- mutex_unlock(&task->signal->cred_guard_mutex);
+ mutex_unlock(&task->signal->exec_update_mutex);
err_task:
if (task)
put_task_struct(task);
@@ -11900,7 +11900,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
/*
* When a child task exits, feed back event values to parent events.
*
- * Can be called with cred_guard_mutex held when called from
+ * Can be called with exec_update_mutex held when called from
* install_exec_creds().
*/
void perf_event_exit_task(struct task_struct *child)
--
1.9.1
This changes do_io_accounting to use the new exec_update_mutex
instead of cred_guard_mutex.
This fixes possible deadlocks when the trace is accessing
/proc/$pid/io for instance.
This should be safe, as the credentials are only used for reading.
Signed-off-by: Bernd Edlinger <bernd.edlinger(a)hotmail.de>
---
fs/proc/base.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index fed76abf..6b13fc4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2861,7 +2861,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
unsigned long flags;
int result;
- result = mutex_lock_killable(&task->signal->cred_guard_mutex);
+ result = mutex_lock_killable(&task->signal->exec_update_mutex);
if (result)
return result;
@@ -2897,7 +2897,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
result = 0;
out_unlock:
- mutex_unlock(&task->signal->cred_guard_mutex);
+ mutex_unlock(&task->signal->exec_update_mutex);
return result;
}
--
1.9.1
This changes lock_trace to use the new exec_update_mutex
instead of cred_guard_mutex.
This fixes possible deadlocks when the trace is accessing
/proc/$pid/stack for instance.
This should be safe, as the credentials are only used for reading,
and task->mm is updated on execve under the new exec_update_mutex.
Signed-off-by: Bernd Edlinger <bernd.edlinger(a)hotmail.de>
---
fs/proc/base.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c7c6427..fed76abf 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -405,11 +405,11 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
static int lock_trace(struct task_struct *task)
{
- int err = mutex_lock_killable(&task->signal->cred_guard_mutex);
+ int err = mutex_lock_killable(&task->signal->exec_update_mutex);
if (err)
return err;
if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
- mutex_unlock(&task->signal->cred_guard_mutex);
+ mutex_unlock(&task->signal->exec_update_mutex);
return -EPERM;
}
return 0;
@@ -417,7 +417,7 @@ static int lock_trace(struct task_struct *task)
static void unlock_trace(struct task_struct *task)
{
- mutex_unlock(&task->signal->cred_guard_mutex);
+ mutex_unlock(&task->signal->exec_update_mutex);
}
#ifdef CONFIG_STACKTRACE
--
1.9.1
This removes an outdated comment in prepare_kernel_cred.
There is no "cred_replace_mutex" any more, so the comment must
go away.
Signed-off-by: Bernd Edlinger <bernd.edlinger(a)hotmail.de>
Reviewed-by: Kees Cook <keescook(a)chromium.org>
---
kernel/cred.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/kernel/cred.c b/kernel/cred.c
index 809a985..71a7926 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -675,8 +675,6 @@ void __init cred_init(void)
* The caller may change these controls afterwards if desired.
*
* Returns the new credentials or NULL if out of memory.
- *
- * Does not take, and does not return holding current->cred_replace_mutex.
*/
struct cred *prepare_kernel_cred(struct task_struct *daemon)
{
--
1.9.1
This removes a duplicate "a" in the comment in process_vm_rw_core.
Signed-off-by: Bernd Edlinger <bernd.edlinger(a)hotmail.de>
Reviewed-by: Kees Cook <keescook(a)chromium.org>
---
mm/process_vm_access.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index de41e83..74e957e 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -206,7 +206,7 @@ static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
if (!mm || IS_ERR(mm)) {
rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
/*
- * Explicitly map EACCES to EPERM as EPERM is a more a
+ * Explicitly map EACCES to EPERM as EPERM is a more
* appropriate error code for process_vw_readv/writev
*/
if (rc == -EACCES)
--
1.9.1
This fixes a deadlock in the tracer when tracing a multi-threaded
application that calls execve while more than one thread are running.
I observed that when running strace on the gcc test suite, it always
blocks after a while, when expect calls execve, because other threads
have to be terminated. They send ptrace events, but the strace is no
longer able to respond, since it is blocked in vm_access.
The deadlock is always happening when strace needs to access the
tracees process mmap, while another thread in the tracee starts to
execve a child process, but that cannot continue until the
PTRACE_EVENT_EXIT is handled and the WIFEXITED event is received:
strace D 0 30614 30584 0x00000000
Call Trace:
__schedule+0x3ce/0x6e0
schedule+0x5c/0xd0
schedule_preempt_disabled+0x15/0x20
__mutex_lock.isra.13+0x1ec/0x520
__mutex_lock_killable_slowpath+0x13/0x20
mutex_lock_killable+0x28/0x30
mm_access+0x27/0xa0
process_vm_rw_core.isra.3+0xff/0x550
process_vm_rw+0xdd/0xf0
__x64_sys_process_vm_readv+0x31/0x40
do_syscall_64+0x64/0x220
entry_SYSCALL_64_after_hwframe+0x44/0xa9
expect D 0 31933 30876 0x80004003
Call Trace:
__schedule+0x3ce/0x6e0
schedule+0x5c/0xd0
flush_old_exec+0xc4/0x770
load_elf_binary+0x35a/0x16c0
search_binary_handler+0x97/0x1d0
__do_execve_file.isra.40+0x5d4/0x8a0
__x64_sys_execve+0x49/0x60
do_syscall_64+0x64/0x220
entry_SYSCALL_64_after_hwframe+0x44/0xa9
This changes mm_access to use the new exec_update_mutex
instead of cred_guard_mutex.
This patch is based on the following patch by Eric W. Biederman:
"[PATCH 0/5] Infrastructure to allow fixing exec deadlocks"
Link: https://lore.kernel.org/lkml/87v9ne5y4y.fsf_-_@x220.int.ebiederm.org/
Signed-off-by: Bernd Edlinger <bernd.edlinger(a)hotmail.de>
Reviewed-by: Kees Cook <keescook(a)chromium.org>
---
kernel/fork.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 036b692..e23ccac 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1224,7 +1224,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
struct mm_struct *mm;
int err;
- err = mutex_lock_killable(&task->signal->cred_guard_mutex);
+ err = mutex_lock_killable(&task->signal->exec_update_mutex);
if (err)
return ERR_PTR(err);
@@ -1234,7 +1234,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
mmput(mm);
mm = ERR_PTR(-EACCES);
}
- mutex_unlock(&task->signal->cred_guard_mutex);
+ mutex_unlock(&task->signal->exec_update_mutex);
return mm;
}
--
1.9.1