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Message-ID: <20221019025710.2482945-1-gongruiqi1@huawei.com>
Date: Wed, 19 Oct 2022 10:57:10 +0800
From: "GONG, Ruiqi" <gongruiqi1@...wei.com>
To: Paul Moore <paul@...l-moore.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Eric Paris <eparis@...isplace.org>
CC: Ondrej Mosnacek <omosnace@...hat.com>, <selinux@...r.kernel.org>,
<linux-security-module@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
"Xiu Jianfeng" <xiujianfeng@...wei.com>, <gongruiqi1@...wei.com>
Subject: [PATCH v2] selinux: use GFP_ATOMIC in convert_context()
The following warning was triggered on a hardware environment:
SELinux: Converting 162 SID table entries...
BUG: sleeping function called from invalid context at __might_sleep+0x60/0x74 0x0
in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 5943, name: tar
CPU: 7 PID: 5943 Comm: tar Tainted: P O 5.10.0 #1
Call trace:
dump_backtrace+0x0/0x1c8
show_stack+0x18/0x28
dump_stack+0xe8/0x15c
___might_sleep+0x168/0x17c
__might_sleep+0x60/0x74
__kmalloc_track_caller+0xa0/0x7dc
kstrdup+0x54/0xac
convert_context+0x48/0x2e4
sidtab_context_to_sid+0x1c4/0x36c
security_context_to_sid_core+0x168/0x238
security_context_to_sid_default+0x14/0x24
inode_doinit_use_xattr+0x164/0x1e4
inode_doinit_with_dentry+0x1c0/0x488
selinux_d_instantiate+0x20/0x34
security_d_instantiate+0x70/0xbc
d_splice_alias+0x4c/0x3c0
ext4_lookup+0x1d8/0x200 [ext4]
__lookup_slow+0x12c/0x1e4
walk_component+0x100/0x200
path_lookupat+0x88/0x118
filename_lookup+0x98/0x130
user_path_at_empty+0x48/0x60
vfs_statx+0x84/0x140
vfs_fstatat+0x20/0x30
__se_sys_newfstatat+0x30/0x74
__arm64_sys_newfstatat+0x1c/0x2c
el0_svc_common.constprop.0+0x100/0x184
do_el0_svc+0x1c/0x2c
el0_svc+0x20/0x34
el0_sync_handler+0x80/0x17c
el0_sync+0x13c/0x140
SELinux: Context system_u:object_r:pssp_rsyslog_log_t:s0:c0 is not valid (left unmapped).
It was found that within a critical section of spin_lock_irqsave in
sidtab_context_to_sid(), convert_context() (hooked by
sidtab_convert_params.func) might cause the process to sleep via
allocating memory with GFP_KERNEL, which is problematic.
As Ondrej pointed out [1], convert_context()/sidtab_convert_params.func
has another caller sidtab_convert_tree(), which is okay with GFP_KERNEL.
Therefore, fix this problem by adding a gfp_t argument for
convert_context()/sidtab_convert_params.func and pass GFP_KERNEL/_ATOMIC
properly in individual callers.
Link: https://lore.kernel.org/all/20221018120111.1474581-1-gongruiqi1@huawei.com/ [1]
Reported-by: Tan Ninghao <tanninghao1@...wei.com>
Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance")
Signed-off-by: GONG, Ruiqi <gongruiqi1@...wei.com>
---
v2: change as Ondrej suggests & redraft commit message
security/selinux/ss/services.c | 5 +++--
security/selinux/ss/sidtab.c | 4 ++--
security/selinux/ss/sidtab.h | 2 +-
3 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index fe5fcf571c56..64a6a37dc36d 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2022,7 +2022,8 @@ static inline int convert_context_handle_invalid_context(
* in `newc'. Verify that the context is valid
* under the new policy.
*/
-static int convert_context(struct context *oldc, struct context *newc, void *p)
+static int convert_context(struct context *oldc, struct context *newc, void *p,
+ gfp_t gfp_flags)
{
struct convert_context_args *args;
struct ocontext *oc;
@@ -2036,7 +2037,7 @@ static int convert_context(struct context *oldc, struct context *newc, void *p)
args = p;
if (oldc->str) {
- s = kstrdup(oldc->str, GFP_KERNEL);
+ s = kstrdup(oldc->str, gfp_flags);
if (!s)
return -ENOMEM;
diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
index a54b8652bfb5..db5cce385bf8 100644
--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -325,7 +325,7 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context,
}
rc = convert->func(context, &dst_convert->context,
- convert->args);
+ convert->args, GFP_ATOMIC);
if (rc) {
context_destroy(&dst->context);
goto out_unlock;
@@ -404,7 +404,7 @@ static int sidtab_convert_tree(union sidtab_entry_inner *edst,
while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
rc = convert->func(&esrc->ptr_leaf->entries[i].context,
&edst->ptr_leaf->entries[i].context,
- convert->args);
+ convert->args, GFP_KERNEL);
if (rc)
return rc;
(*pos)++;
diff --git a/security/selinux/ss/sidtab.h b/security/selinux/ss/sidtab.h
index 4eff0e49dcb2..9fce0d553fe2 100644
--- a/security/selinux/ss/sidtab.h
+++ b/security/selinux/ss/sidtab.h
@@ -65,7 +65,7 @@ struct sidtab_isid_entry {
};
struct sidtab_convert_params {
- int (*func)(struct context *oldc, struct context *newc, void *args);
+ int (*func)(struct context *oldc, struct context *newc, void *args, gfp_t gfp_flags);
void *args;
struct sidtab *target;
};
--
2.25.1
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