The patch titled
exec: fix set_binfmt() vs sys_delete_module() race
has been added to the -mm tree. Its filename is
exec-fix-set_binfmt-vs-sys_delete_module-race.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: exec: fix set_binfmt() vs sys_delete_module() race
From: Oleg Nesterov <oleg@xxxxxxxxxx>
sys_delete_module() can set MODULE_STATE_GOING after
search_binary_handler() does try_module_get(). In this case
set_binfmt()->try_module_get() fails but since none of the callers
check the returned error, the task will run with the wrong old
->binfmt.
The proper fix should change all ->load_binary() methods, but we can
rely on fact that the caller must hold a reference to binfmt->module
and use __module_get() which never fails.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Hiroshi Shimamoto <h-shimamoto@xxxxxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 17 ++++++++---------
include/linux/binfmts.h | 2 +-
2 files changed, 9 insertions(+), 10 deletions(-)
diff -puN fs/exec.c~exec-fix-set_binfmt-vs-sys_delete_module-race fs/exec.c
--- a/fs/exec.c~exec-fix-set_binfmt-vs-sys_delete_module-race
+++ a/fs/exec.c
@@ -1384,18 +1384,17 @@ out_ret:
return retval;
}
-int set_binfmt(struct linux_binfmt *new)
+/*
+ * The caller, ->load_binary(), must hold a reference to ->module.
+ */
+void set_binfmt(struct linux_binfmt *new)
{
- struct linux_binfmt *old = current->binfmt;
+ if (current->binfmt)
+ module_put(current->binfmt->module);
- if (new) {
- if (!try_module_get(new->module))
- return -1;
- }
current->binfmt = new;
- if (old)
- module_put(old->module);
- return 0;
+ if (new)
+ __module_get(new->module);
}
EXPORT_SYMBOL(set_binfmt);
diff -puN include/linux/binfmts.h~exec-fix-set_binfmt-vs-sys_delete_module-race include/linux/binfmts.h
--- a/include/linux/binfmts.h~exec-fix-set_binfmt-vs-sys_delete_module-race
+++ a/include/linux/binfmts.h
@@ -119,7 +119,7 @@ extern int bprm_mm_init(struct linux_bin
extern int copy_strings_kernel(int argc,char ** argv,struct linux_binprm *bprm);
extern void install_exec_creds(struct linux_binprm *bprm);
extern void do_coredump(long signr, int exit_code, struct pt_regs *regs);
-extern int set_binfmt(struct linux_binfmt *new);
+extern void set_binfmt(struct linux_binfmt *new);
extern void free_bprm(struct linux_binprm *);
#endif /* __KERNEL__ */
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
linux-next.patch
getrusage-fill-ru_maxrss-value.patch
getrusage-fill-ru_maxrss-value-update.patch
proc_flush_task-flush-proc-tid-task-pid-when-a-sub-thread-exits.patch
ptrace-__ptrace_detach-do-__wake_up_parent-if-we-reap-the-tracee.patch
do_wait-wakeup-optimization-shift-security_task_wait-from-eligible_child-to-wait_consider_task.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup-selinux_bprm_committed_creds-use-__wake_up_parent.patch
do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch
do_wait-optimization-do-not-place-sub-threads-on-task_struct-children-list.patch
wait_consider_task-kill-parent-argument.patch
do_wait-fix-sys_waitid-specific-behaviour.patch
wait_noreap_copyout-check-for-wo_info-=-null.patch
signals-tracehook_notify_jctl-change.patch
utrace-core.patch
exec-fix-set_binfmt-vs-sys_delete_module-race.patch
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