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Old 03-26-2012, 01:28 AM
Tim Gardner
 
Default kmod: make __request_module() killable

From: Oleg Nesterov <oleg@redhat.com>

BugLink: http://bugs.launchpad.net/bugs/963685

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 <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 1cc684ab75123efe7ff446eb821d44375ba8fa30)

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
kernel/kmod.c | 26 ++++++++++++++++++++++++--
1 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index ca9d2b1..fecaf21 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -58,6 +58,12 @@ static DEFINE_SPINLOCK(umh_sysctl_lock);
*/
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[] = {
@@ -67,10 +73,26 @@ 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;
}

/**
--
1.7.9.1


--
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kernel-team@lists.ubuntu.com
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Old 03-26-2012, 02:53 PM
Tim Gardner
 
Default kmod: make __request_module() killable

From: Oleg Nesterov <oleg@redhat.com>

BugLink: http://bugs.launchpad.net/bugs/963685

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 <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 1cc684ab75123efe7ff446eb821d44375ba8fa30)

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
kernel/kmod.c | 26 ++++++++++++++++++++++++--
1 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 1b58236..dbb403b 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -50,6 +50,12 @@ static struct workqueue_struct *khelper_wq;
*/
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[] = {
@@ -59,10 +65,26 @@ 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;
}

/**
--
1.7.9.1


--
kernel-team mailing list
kernel-team@lists.ubuntu.com
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Old 03-26-2012, 06:01 PM
Tim Gardner
 
Default kmod: make __request_module() killable

From: Oleg Nesterov <oleg@redhat.com>

BugLink: http://bugs.launchpad.net/bugs/963685

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 <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 1cc684ab75123efe7ff446eb821d44375ba8fa30)

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
kernel/kmod.c | 26 ++++++++++++++++++++++++--
1 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 7a95c302..f3276df 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -53,6 +53,12 @@ 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[] = {
@@ -62,10 +68,26 @@ 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;
}

/**
--
1.7.9.1


--
kernel-team mailing list
kernel-team@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/kernel-team
 

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