From 1cc684ab75123efe7ff446eb821d44375ba8fa30 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 23 Mar 2012 15:02:50 -0700 Subject: kmod: make __request_module() killable As Tetsuo Handa pointed out, request_module() can stress the system while the oom-killed caller sleeps in TASK_UNINTERRUPTIBLE. The task T uses "almost all" memory, then it does something which triggers request_module(). Say, it can simply call sys_socket(). This in turn needs more memory and leads to OOM. oom-killer correctly chooses T and kills it, but this can't help because it sleeps in TASK_UNINTERRUPTIBLE and after that oom-killer becomes "disabled" by the TIF_MEMDIE task T. Make __request_module() killable. The only necessary change is that call_modprobe() should kmalloc argv and module_name, they can't live in the stack if we use UMH_KILLABLE. This memory is freed via call_usermodehelper_freeinfo()->cleanup. Reported-by: Tetsuo Handa Signed-off-by: Oleg Nesterov Cc: Rusty Russell Cc: Tejun Heo Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kmod.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) (limited to 'kernel/kmod.c') diff --git a/kernel/kmod.c b/kernel/kmod.c index 56a29e812ff..957a7aab8eb 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -60,6 +60,12 @@ static DECLARE_RWSEM(umhelper_sem); */ char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; +static void free_modprobe_argv(struct subprocess_info *info) +{ + kfree(info->argv[3]); /* check call_modprobe() */ + kfree(info->argv); +} + static int call_modprobe(char *module_name, int wait) { static char *envp[] = { @@ -69,10 +75,26 @@ static int call_modprobe(char *module_name, int wait) NULL }; - char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; + char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL); + if (!argv) + goto out; + + module_name = kstrdup(module_name, GFP_KERNEL); + if (!module_name) + goto free_argv; + + argv[0] = modprobe_path; + argv[1] = "-q"; + argv[2] = "--"; + argv[3] = module_name; /* check free_modprobe_argv() */ + argv[4] = NULL; return call_usermodehelper_fns(modprobe_path, argv, envp, - wait, NULL, NULL, NULL); + wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL); +free_argv: + kfree(argv); +out: + return -ENOMEM; } /** -- cgit v1.2.3