[PATCH] driver core: Fix a null-ptr-deref in module_add_driver()

[PATCH] driver core: Fix a null-ptr-deref in module_add_driver()

[Jinjie Ruan]

Inject fault while probing of-fpga-region, if kasprintf() fails in
module_add_driver(), the second sysfs_remove_link() in exit path will cause
null-ptr-deref as below because kernfs_name_hash() will call strlen() with
NULL driver_name.

Fix it by releasing resources based on the exit path sequence.

	 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
	 Mem abort info:
	   ESR = 0x0000000096000005
	   EC = 0x25: DABT (current EL), IL = 32 bits
	   SET = 0, FnV = 0
	   EA = 0, S1PTW = 0
	   FSC = 0x05: level 1 translation fault
	 Data abort info:
	   ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
	   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
	   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
	 [dfffffc000000000] address between user and kernel address ranges
	 Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
	 Dumping ftrace buffer:
	    (ftrace buffer empty)
	 Modules linked in: of_fpga_region(+) fpga_region fpga_bridge cfg80211 rfkill 8021q garp mrp stp llc ipv6 [last unloaded: of_fpga_region]
	 CPU: 2 UID: 0 PID: 2036 Comm: modprobe Not tainted 6.11.0-rc2-g6a0e38264012 #295
	 Hardware name: linux,dummy-virt (DT)
	 pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
	 pc : strlen+0x24/0xb0
	 lr : kernfs_name_hash+0x1c/0xc4
	 sp : ffffffc081f97380
	 x29: ffffffc081f97380 x28: ffffffc081f97b90 x27: ffffff80c821c2a0
	 x26: ffffffedac0be418 x25: 0000000000000000 x24: ffffff80c09d2000
	 x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000000
	 x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000001840
	 x17: 0000000000000000 x16: 0000000000000000 x15: 1ffffff8103f2e42
	 x14: 00000000f1f1f1f1 x13: 0000000000000004 x12: ffffffb01812d61d
	 x11: 1ffffff01812d61c x10: ffffffb01812d61c x9 : dfffffc000000000
	 x8 : 0000004fe7ed29e4 x7 : ffffff80c096b0e7 x6 : 0000000000000001
	 x5 : ffffff80c096b0e0 x4 : 1ffffffdb990efa2 x3 : 0000000000000000
	 x2 : 0000000000000000 x1 : dfffffc000000000 x0 : 0000000000000000
	 Call trace:
	  strlen+0x24/0xb0
	  kernfs_name_hash+0x1c/0xc4
	  kernfs_find_ns+0x118/0x2e8
	  kernfs_remove_by_name_ns+0x80/0x100
	  sysfs_remove_link+0x74/0xa8
	  module_add_driver+0x278/0x394
	  bus_add_driver+0x1f0/0x43c
	  driver_register+0xf4/0x3c0
	  __platform_driver_register+0x60/0x88
	  of_fpga_region_init+0x20/0x1000 [of_fpga_region]
	  do_one_initcall+0x110/0x788
	  do_init_module+0x1dc/0x5c8
	  load_module+0x3c38/0x4cac
	  init_module_from_file+0xd4/0x128
	  idempotent_init_module+0x2cc/0x528
	  __arm64_sys_finit_module+0xac/0x100
	  invoke_syscall+0x6c/0x258
	  el0_svc_common.constprop.0+0x160/0x22c
	  do_el0_svc+0x44/0x5c
	  el0_svc+0x48/0xb8
	  el0t_64_sync_handler+0x13c/0x158
	  el0t_64_sync+0x190/0x194
	 Code: f2fbffe1 a90157f4 12000802 aa0003f5 (38e16861)
	 ---[ end trace 0000000000000000 ]---
	 Kernel panic - not syncing: Oops: Fatal exception

Fixes: 85d2b0aa1703 ("module: don't ignore sysfs_create_link() failures")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 drivers/base/module.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/base/module.c b/drivers/base/module.c
index f742ad2a21da..c4eaa1158d54 100644
--- a/drivers/base/module.c
+++ b/drivers/base/module.c
@@ -66,27 +66,31 @@ int module_add_driver(struct module *mod, const struct device_driver *drv)
 	driver_name = make_driver_name(drv);
 	if (!driver_name) {
 		ret = -ENOMEM;
-		goto out;
+		goto out_remove_kobj;
 	}
 
 	module_create_drivers_dir(mk);
 	if (!mk->drivers_dir) {
 		ret = -EINVAL;
-		goto out;
+		goto out_free_driver_name;
 	}
 
 	ret = sysfs_create_link(mk->drivers_dir, &drv->p->kobj, driver_name);
 	if (ret)
-		goto out;
+		goto out_remove_drivers_dir;
 
 	kfree(driver_name);
 
 	return 0;
-out:
-	sysfs_remove_link(&drv->p->kobj, "module");
+
+out_remove_drivers_dir:
 	sysfs_remove_link(mk->drivers_dir, driver_name);
+
+out_free_driver_name:
 	kfree(driver_name);
 
+out_remove_kobj:
+	sysfs_remove_link(&drv->p->kobj, "module");
 	return ret;
 }
 
-- 
2.34.1

Re: [PATCH] driver core: Fix a null-ptr-deref in module_add_driver()

[Markus Elfring]

> Inject fault while probing of-fpga-region, if kasprintf() fails in
> module_add_driver(), the second sysfs_remove_link() in exit path will cause
> null-ptr-deref as below because kernfs_name_hash() will call strlen() with
> NULL driver_name.
…

How do you think about to use the term “null pointer dereference”
for the commit message (and summary phrase)?


…
> +++ b/drivers/base/module.c
> @@ -66,27 +66,31 @@ int module_add_driver(struct module *mod, const struct device_driver *drv)
…
>  	sysfs_remove_link(mk->drivers_dir, driver_name);
> +
> +out_free_driver_name:
>  	kfree(driver_name);
>
> +out_remove_kobj:
> +	sysfs_remove_link(&drv->p->kobj, "module");
…

I suggest to omit two blank lines here.

Regards,
Markus

Re: [PATCH] driver core: Fix a null-ptr-deref in module_add_driver()

[Greg Kroah-Hartman]

On Mon, Aug 12, 2024 at 12:18:17PM +0200, Markus Elfring wrote:
> > Inject fault while probing of-fpga-region, if kasprintf() fails in
> > module_add_driver(), the second sysfs_remove_link() in exit path will cause
> > null-ptr-deref as below because kernfs_name_hash() will call strlen() with
> > NULL driver_name.
> …
> 
> How do you think about to use the term “null pointer dereference”
> for the commit message (and summary phrase)?
> 
> 
> …
> > +++ b/drivers/base/module.c
> > @@ -66,27 +66,31 @@ int module_add_driver(struct module *mod, const struct device_driver *drv)
> …
> >  	sysfs_remove_link(mk->drivers_dir, driver_name);
> > +
> > +out_free_driver_name:
> >  	kfree(driver_name);
> >
> > +out_remove_kobj:
> > +	sysfs_remove_link(&drv->p->kobj, "module");
> …
> 
> I suggest to omit two blank lines here.


Hi,

This is the semi-friendly patch-bot of Greg Kroah-Hartman.

Markus, you seem to have sent a nonsensical or otherwise pointless
review comment to a patch submission on a Linux kernel developer mailing
list.  I strongly suggest that you not do this anymore.  Please do not
bother developers who are actively working to produce patches and
features with comments that, in the end, are a waste of time.

Patch submitter, please ignore Markus's suggestion; you do not need to
follow it at all.  The person/bot/AI that sent it is being ignored by
almost all Linux kernel maintainers for having a persistent pattern of
behavior of producing distracting and pointless commentary, and
inability to adapt to feedback.  Please feel free to also ignore emails
from them.

thanks,

greg k-h's patch email bot