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authorReinette Chatre <reinette.chatre@intel.com>2020-03-17 09:26:45 -0700
committerBorislav Petkov <bp@suse.de>2020-04-17 16:26:23 +0200
commitb0151da52a6d4f3951ea24c083e7a95977621436 (patch)
tree3e76af6be230d15d2b3de1eaacb664fbf2348ec3
parent3ab0762d1edfda6ccbc08f636acab42c103c299f (diff)
downloadlinux-b0151da52a6d4f3951ea24c083e7a95977621436.tar.bz2
x86/resctrl: Fix invalid attempt at removing the default resource group
The default resource group ("rdtgroup_default") is associated with the root of the resctrl filesystem and should never be removed. New resource groups can be created as subdirectories of the resctrl filesystem and they can be removed from user space. There exists a safeguard in the directory removal code (rdtgroup_rmdir()) that ensures that only subdirectories can be removed by testing that the directory to be removed has to be a child of the root directory. A possible deadlock was recently fixed with 334b0f4e9b1b ("x86/resctrl: Fix a deadlock due to inaccurate reference"). This fix involved associating the private data of the "mon_groups" and "mon_data" directories to the resource group to which they belong instead of NULL as before. A consequence of this change was that the original safeguard code preventing removal of "mon_groups" and "mon_data" found in the root directory failed resulting in attempts to remove the default resource group that ends in a BUG: kernel BUG at mm/slub.c:3969! invalid opcode: 0000 [#1] SMP PTI Call Trace: rdtgroup_rmdir+0x16b/0x2c0 kernfs_iop_rmdir+0x5c/0x90 vfs_rmdir+0x7a/0x160 do_rmdir+0x17d/0x1e0 do_syscall_64+0x55/0x1d0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fix this by improving the directory removal safeguard to ensure that subdirectories of the resctrl root directory can only be removed if they are a child of the resctrl filesystem's root _and_ not associated with the default resource group. Fixes: 334b0f4e9b1b ("x86/resctrl: Fix a deadlock due to inaccurate reference") Reported-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/884cbe1773496b5dbec1b6bd11bb50cffa83603d.1584461853.git.reinette.chatre@intel.com
-rw-r--r--arch/x86/kernel/cpu/resctrl/rdtgroup.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 064e9ef44cd6..9d4e73a9b5a9 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3072,7 +3072,8 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
* If the rdtgroup is a mon group and parent directory
* is a valid "mon_groups" directory, remove the mon group.
*/
- if (rdtgrp->type == RDTCTRL_GROUP && parent_kn == rdtgroup_default.kn) {
+ if (rdtgrp->type == RDTCTRL_GROUP && parent_kn == rdtgroup_default.kn &&
+ rdtgrp != &rdtgroup_default) {
if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP ||
rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
ret = rdtgroup_ctrl_remove(kn, rdtgrp);