EDAC: Fix global-out-of-bounds write when setting edac_mc_poll_msec [Linux 4.9.187]

This Linux kernel change "EDAC: Fix global-out-of-bounds write when setting edac_mc_poll_msec" is included in the Linux 4.9.187 release. This change is authored by Eiichi Tsukata <devel [at] etsukata.com> on Wed Jun 26 14:40:11 2019 +0900. The commit for this change in Linux stable tree is 8328587 (patch) which is from upstream commit d8655e7. The same Linux upstream change may have been applied to various maintained Linux releases and you can find all Linux releases containing changes from upstream d8655e7.

EDAC: Fix global-out-of-bounds write when setting edac_mc_poll_msec

[ Upstream commit d8655e7630dafa88bc37f101640e39c736399771 ]

Commit 9da21b1509d8 ("EDAC: Poll timeout cannot be zero, p2") assumes
edac_mc_poll_msec to be unsigned long, but the type of the variable still
remained as int. Setting edac_mc_poll_msec can trigger out-of-bounds
write.

Reproducer:

  # echo 1001 > /sys/module/edac_core/parameters/edac_mc_poll_msec

KASAN report:

  BUG: KASAN: global-out-of-bounds in edac_set_poll_msec+0x140/0x150
  Write of size 8 at addr ffffffffb91b2d00 by task bash/1996

  CPU: 1 PID: 1996 Comm: bash Not tainted 5.2.0-rc6+ #23
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-2.fc30 04/01/2014
  Call Trace:
   dump_stack+0xca/0x13e
   print_address_description.cold+0x5/0x246
   __kasan_report.cold+0x75/0x9a
   ? edac_set_poll_msec+0x140/0x150
   kasan_report+0xe/0x20
   edac_set_poll_msec+0x140/0x150
   ? dimmdev_location_show+0x30/0x30
   ? vfs_lock_file+0xe0/0xe0
   ? _raw_spin_lock+0x87/0xe0
   param_attr_store+0x1b5/0x310
   ? param_array_set+0x4f0/0x4f0
   module_attr_store+0x58/0x80
   ? module_attr_show+0x80/0x80
   sysfs_kf_write+0x13d/0x1a0
   kernfs_fop_write+0x2bc/0x460
   ? sysfs_kf_bin_read+0x270/0x270
   ? kernfs_notify+0x1f0/0x1f0
   __vfs_write+0x81/0x100
   vfs_write+0x1e1/0x560
   ksys_write+0x126/0x250
   ? __ia32_sys_read+0xb0/0xb0
   ? do_syscall_64+0x1f/0x390
   do_syscall_64+0xc1/0x390
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7fa7caa5e970
  Code: 73 01 c3 48 8b 0d 28 d5 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 99 2d 2c 00 00 75 10 b8 01 00 00 00 04
  RSP: 002b:00007fff6acfdfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
  RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007fa7caa5e970
  RDX: 0000000000000005 RSI: 0000000000e95c08 RDI: 0000000000000001
  RBP: 0000000000e95c08 R08: 00007fa7cad1e760 R09: 00007fa7cb36a700
  R10: 0000000000000073 R11: 0000000000000246 R12: 0000000000000005
  R13: 0000000000000001 R14: 00007fa7cad1d600 R15: 0000000000000005

  The buggy address belongs to the variable:
   edac_mc_poll_msec+0x0/0x40

  Memory state around the buggy address:
   ffffffffb91b2c00: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa
   ffffffffb91b2c80: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa
  >ffffffffb91b2d00: 04 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa
                     ^
   ffffffffb91b2d80: 04 fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
   ffffffffb91b2e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Fix it by changing the type of edac_mc_poll_msec to unsigned int.
The reason why this patch adopts unsigned int rather than unsigned long
is msecs_to_jiffies() assumes arg to be unsigned int. We can avoid
integer conversion bugs and unsigned int will be large enough for
edac_mc_poll_msec.

Reviewed-by: James Morse <james.morse@arm.com>
Fixes: 9da21b1509d8 ("EDAC: Poll timeout cannot be zero, p2")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

There are 18 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/edac/edac_mc_sysfs.c | 16 ++++++++--------
 drivers/edac/edac_module.h   |  2 +-
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 203ebe3..d596411 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -26,7 +26,7 @@
 static int edac_mc_log_ue = 1;
 static int edac_mc_log_ce = 1;
 static int edac_mc_panic_on_ue;
-static int edac_mc_poll_msec = 1000;
+static unsigned int edac_mc_poll_msec = 1000;

 /* Getter functions for above */
 int edac_mc_get_log_ue(void)
@@ -45,30 +45,30 @@ int edac_mc_get_panic_on_ue(void)
 }

 /* this is temporary */
-int edac_mc_get_poll_msec(void)
+unsigned int edac_mc_get_poll_msec(void)
 {
    return edac_mc_poll_msec;
 }

 static int edac_set_poll_msec(const char *val, struct kernel_param *kp)
 {
-   unsigned long l;
+   unsigned int i;
    int ret;

    if (!val)
        return -EINVAL;

-   ret = kstrtoul(val, 0, &l);
+   ret = kstrtouint(val, 0, &i);
    if (ret)
        return ret;

-   if (l < 1000)
+   if (i < 1000)
        return -EINVAL;

-   *((unsigned long *)kp->arg) = l;
+   *((unsigned int *)kp->arg) = i;

    /* notify edac_mc engine to reset the poll period */
-   edac_mc_reset_delay_period(l);
+   edac_mc_reset_delay_period(i);

    return 0;
 }
@@ -82,7 +82,7 @@ static int edac_set_poll_msec(const char *val, struct kernel_param *kp)
 module_param(edac_mc_log_ce, int, 0644);
 MODULE_PARM_DESC(edac_mc_log_ce,
         "Log correctable error to console: 0=off 1=on");
-module_param_call(edac_mc_poll_msec, edac_set_poll_msec, param_get_int,
+module_param_call(edac_mc_poll_msec, edac_set_poll_msec, param_get_uint,
          &edac_mc_poll_msec, 0644);
 MODULE_PARM_DESC(edac_mc_poll_msec, "Polling period in milliseconds");

diff --git a/drivers/edac/edac_module.h b/drivers/edac/edac_module.h
index cfaacb9..c36f9f7 100644
--- a/drivers/edac/edac_module.h
+++ b/drivers/edac/edac_module.h
@@ -33,7 +33,7 @@ extern int edac_create_sysfs_mci_device(struct mem_ctl_info *mci,
 extern int edac_mc_get_log_ce(void);
 extern int edac_mc_get_panic_on_ue(void);
 extern int edac_get_poll_msec(void);
-extern int edac_mc_get_poll_msec(void);
+extern unsigned int edac_mc_get_poll_msec(void);

 unsigned edac_dimm_info_location(struct dimm_info *dimm, char *buf,
                 unsigned len);

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