[PATCH][next] sched/debug: fix memory corruption caused by multiple small reads of flags
From: Colin King
Date: Thu Oct 29 2020 - 11:11:16 EST
From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Reading /proc/sys/kernel/sched_domain/cpu*/domain0/flags mutliple times
with small reads causes oopses with slub corruption issues because the kfree is
free'ing an offset from a previous allocation. Fix this by adding in a new
pointer 'buf' for the allocation and kfree and use the temporary pointer tmp
to handle memory copies of the buf offsets.
Detected by running 'stress-ng --procfs 0' on 5.10-rc1; example splat:
[ 984.137351] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-128' (offset 127, size 3)!
[ 984.148917] ------------[ cut here ]------------
[ 984.154089] kernel BUG at mm/usercopy.c:99!
[ 984.158813] invalid opcode: 0000 [#1] SMP PTI
[ 984.163771] CPU: 0 PID: 3031471 Comm: stress-ng-procf Tainted: G I 5.10.0-rc1 #1
[ 984.173483] Hardware name: IBM IBM System X3250 M4 -[2583AC1]-/00D3729, BIOS -[JQE158AUS-1.05]- 07/23/2013
[ 984.184260] RIP: 0010:usercopy_abort+0x74/0x76
[ 984.189219] Code: 67 5c 8b 51 48 0f 45 d6 49 c7 c3 73 f7 5f 8b 4c 89 d1 57 48 c7 c6 68 57 5e 8b 48 c7 c7 38 f8 5f 8b 49 0f 45 f3 e8 13 71 ff ff <0f> 0b 4c 89 e1 49 89 d8 44 89 ea 31 f6 48 29 c1 48 c7 c7 b5 f7 5f
[ 984.210177] RSP: 0018:ffff9c1f007b3dc0 EFLAGS: 00010286
[ 984.216000] RAX: 0000000000000066 RBX: 0000000000000003 RCX: 0000000000000000
[ 984.223965] RDX: ffff911f37c27e20 RSI: ffff911f37c19050 RDI: ffff911f37c19050
[ 984.231929] RBP: ffff911e04cd1f82 R08: 0000000000000000 R09: 0000000000000000
[ 984.239893] R10: ffff9c1f007b3bf8 R11: ffffffff8bd711a8 R12: ffff911e04cd1f7f
[ 984.247857] R13: 0000000000000001 R14: 0000000000000003 R15: ffff911e009b19c0
[ 984.255821] FS: 00007fbabb42b180(0000) GS:ffff911f37c00000(0000) knlGS:0000000000000000
[ 984.264915] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 984.271520] CR2: 00007fbabb7ef000 CR3: 000000014e296001 CR4: 00000000001706f0
[ 984.279683] Call Trace:
[ 984.282581] __check_heap_object+0xe0/0x110
[ 984.287405] __check_object_size+0x136/0x150
[ 984.292347] proc_sys_call_handler+0x167/0x250
[ 984.297565] new_sync_read+0x108/0x180
[ 984.302082] vfs_read+0x174/0x1d0
[ 984.306126] ksys_read+0x58/0xd0
[ 984.310022] do_syscall_64+0x33/0x40
[ 984.314277] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 984.320201] RIP: 0033:0x7fbabb6099ac
[ 984.324514] Code: ec 28 48 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 89 fc ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 34 44 89 c7 48 89 44 24 08 e8 bf fc ff ff 48
[ 984.346368] RSP: 002b:00007fff47397340 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 984.355402] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbabb6099ac
[ 984.363971] RDX: 0000000000000060 RSI: 00007fff47397390 RDI: 0000000000000006
[ 984.372583] RBP: 0000000000000006 R08: 0000000000000000 R09: 0000000000000000
[ 984.381093] R10: 00000000000fa2b4 R11: 0000000000000246 R12: 0000000000000003
[ 984.389577] R13: 00007fff473a3630 R14: 0000000000001000 R15: 0000000000000060
[ 984.398087] Modules linked in: binfmt_misc rfkill sunrpc intel_rapl_msr intel_rapl_common x86_pkg_temp_thermal mgag200 intel_powerclamp iTCO_wdt i2c_algo_bit coretemp intel_pmc_bxt cdc_ether gpio_ich drm_kms_helper iTCO_vendor_support usbnet mii cec rapl ipmi_ssif i2c_i801 intel_cstate e1000e intel_uncore ie31200_edac pcspkr ipmi_si i2c_smbus lpc_ich ipmi_devintf ipmi_msghandler drm ip_tables xfs crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel ata_generic pata_acpi wmi
[ 984.449316] ---[ end trace d44739bb135b1e63 ]---
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209919
Reported-by: Jeff Bastian <jbastian@xxxxxxxxxx>
Fixes: 5b9f8ff7b320 ("sched/debug: Output SD flag names rather than their values")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
---
kernel/sched/debug.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 0655524..2357921 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -251,7 +251,7 @@ static int sd_ctl_doflags(struct ctl_table *table, int write,
unsigned long flags = *(unsigned long *)table->data;
size_t data_size = 0;
size_t len = 0;
- char *tmp;
+ char *tmp, *buf;
int idx;
if (write)
@@ -269,17 +269,17 @@ static int sd_ctl_doflags(struct ctl_table *table, int write,
return 0;
}
- tmp = kcalloc(data_size + 1, sizeof(*tmp), GFP_KERNEL);
- if (!tmp)
+ buf = kcalloc(data_size + 1, sizeof(*buf), GFP_KERNEL);
+ if (!buf)
return -ENOMEM;
for_each_set_bit(idx, &flags, __SD_FLAG_CNT) {
char *name = sd_flag_debug[idx].name;
- len += snprintf(tmp + len, strlen(name) + 2, "%s ", name);
+ len += snprintf(buf + len, strlen(name) + 2, "%s ", name);
}
- tmp += *ppos;
+ tmp = buf + *ppos;
len -= *ppos;
if (len > *lenp)
@@ -294,7 +294,7 @@ static int sd_ctl_doflags(struct ctl_table *table, int write,
*lenp = len;
*ppos += len;
- kfree(tmp);
+ kfree(buf);
return 0;
}
--
2.7.4