CVE-2019-11811: Use After Free (CWE-416)
value: An issue was discovered in the Linux kernel before 5.0.4. There is a use-after-free upon attempted read access to /proc/ioports after the ipmi_si module is removed, related to drivers/char/ipmi/ipmi_si_intf.c, drivers/char/ipmi/ipmi_si_mem_io.c, and drivers/char/ipmi/ipmi_si_port_io.c.
CWE description: The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
CVSS v3 base score: 7
Published: 2019-05-07T14:29Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: drivers/char/ipmi/ipmi_si_intf.c, drivers/char/ipmi/ipmi_si_mem_io.c, drivers/char/ipmi/ipmi_si_port_io.c
Commit date: 2019-02-09 19:48:41 -0600
Commit message: ipmi_si: fix use-after-free of resource->name

When we excute the following commands, we got oops
rmmod ipmi_si
cat /proc/ioports

[ 1623.482380] Unable to handle kernel paging request at virtual address ffff00000901d478
[ 1623.482382] Mem abort info:
[ 1623.482383]   ESR = 0x96000007
[ 1623.482385]   Exception class = DABT (current EL), IL = 32 bits
[ 1623.482386]   SET = 0, FnV = 0
[ 1623.482387]   EA = 0, S1PTW = 0
[ 1623.482388] Data abort info:
[ 1623.482389]   ISV = 0, ISS = 0x00000007
[ 1623.482390]   CM = 0, WnR = 0
[ 1623.482393] swapper pgtable: 4k pages, 48-bit VAs, pgdp = 00000000d7d94a66
[ 1623.482395] [ffff00000901d478] pgd=000000dffbfff003, pud=000000dffbffe003, pmd=0000003f5d06e003, pte=0000000000000000
[ 1623.482399] Internal error: Oops: 96000007 [#1] SMP
[ 1623.487407] Modules linked in: ipmi_si(E) nls_utf8 isofs rpcrdma ib_iser ib_srpt target_core_mod ib_srp scsi_transport_srp ib_ipoib rdma_ucm ib_umad rdma_cm ib_cm dm_mirror dm_region_hash dm_log iw_cm dm_mod aes_ce_blk crypto_simd cryptd aes_ce_cipher ses ghash_ce sha2_ce enclosure sha256_arm64 sg sha1_ce hisi_sas_v2_hw hibmc_drm sbsa_gwdt hisi_sas_main ip_tables mlx5_ib ib_uverbs marvell ib_core mlx5_core ixgbe mdio hns_dsaf ipmi_devintf hns_enet_drv ipmi_msghandler hns_mdio [last unloaded: ipmi_si]
[ 1623.532410] CPU: 30 PID: 11438 Comm: cat Kdump: loaded Tainted: G            E     5.0.0-rc3+ #168
[ 1623.541498] Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.37 11/21/2017
[ 1623.548822] pstate: a0000005 (NzCv daif -PAN -UAO)
[ 1623.553684] pc : string+0x28/0x98
[ 1623.557040] lr : vsnprintf+0x368/0x5e8
[ 1623.560837] sp : ffff000013213a80
[ 1623.564191] x29: ffff000013213a80 x28: ffff00001138abb5
[ 1623.569577] x27: ffff000013213c18 x26: ffff805f67d06049
[ 1623.574963] x25: 0000000000000000 x24: ffff00001138abb5
[ 1623.580349] x23: 0000000000000fb7 x22: ffff0000117ed000
[ 1623.585734] x21: ffff000011188fd8 x20: ffff805f67d07000
[ 1623.591119] x19: ffff805f67d06061 x18: ffffffffffffffff
[ 1623.596505] x17: 0000000000000200 x16: 0000000000000000
[ 1623.601890] x15: ffff0000117ed748 x14: ffff805f67d07000
[ 1623.607276] x13: ffff805f67d0605e x12: 0000000000000000
[ 1623.612661] x11: 0000000000000000 x10: 0000000000000000
[ 1623.618046] x9 : 0000000000000000 x8 : 000000000000000f
[ 1623.623432] x7 : ffff805f67d06061 x6 : fffffffffffffffe
[ 1623.628817] x5 : 0000000000000012 x4 : ffff00000901d478
[ 1623.634203] x3 : ffff0a00ffffff04 x2 : ffff805f67d07000
[ 1623.639588] x1 : ffff805f67d07000 x0 : ffffffffffffffff
[ 1623.644974] Process cat (pid: 11438, stack limit = 0x000000008d4cbc10)
[ 1623.651592] Call trace:
[ 1623.654068]  string+0x28/0x98
[ 1623.657071]  vsnprintf+0x368/0x5e8
[ 1623.660517]  seq_vprintf+0x70/0x98
[ 1623.668009]  seq_printf+0x7c/0xa0
[ 1623.675530]  r_show+0xc8/0xf8
[ 1623.682558]  seq_read+0x330/0x440
[ 1623.689877]  proc_reg_read+0x78/0xd0
[ 1623.697346]  __vfs_read+0x60/0x1a0
[ 1623.704564]  vfs_read+0x94/0x150
[ 1623.711339]  ksys_read+0x6c/0xd8
[ 1623.717939]  __arm64_sys_read+0x24/0x30
[ 1623.725077]  el0_svc_common+0x120/0x148
[ 1623.732035]  el0_svc_handler+0x30/0x40
[ 1623.738757]  el0_svc+0x8/0xc
[ 1623.744520] Code: d1000406 aa0103e2 54000149 b4000080 (39400085)
[ 1623.753441] ---[ end trace f91b6a4937de9835 ]---
[ 1623.760871] Kernel panic - not syncing: Fatal exception
[ 1623.768935] SMP: stopping secondary CPUs
[ 1623.775718] Kernel Offset: disabled
[ 1623.781998] CPU features: 0x002,21006008
[ 1623.788777] Memory Limit: none
[ 1623.798329] Starting crashdump kernel...
[ 1623.805202] Bye!

If io_setup is called successful in try_smi_init() but try_smi_init()
goes out_err before calling ipmi_register_smi(), so ipmi_unregister_smi()
will not be called while removing module. It leads to the resource that
allocated in io_setup() can not be freed, but the name(DEVICE_NAME) of
resource is freed while removing the module. It causes use-after-free
when cat /proc/ioports.

Fix this by calling io_cleanup() while try_smi_init() goes to out_err.
and don't call io_cleanup() until io_setup() returns successful to avoid
warning prints.

Fixes: 93c303d2045b ("ipmi_si: Clean up shutdown a bit")
Cc: stable@vger.kernel.org
Reported-by: NuoHan Qiao <qiaonuohan@huawei.com>
Suggested-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

Diff: diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index dc8603d34320..f1b9fda6b9df 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -2083,10 +2083,15 @@ static int try_smi_init(struct smi_info *new_smi)
 		 si_to_str[new_smi->io.si_type]);
 
 	WARN_ON(new_smi->io.dev->init_name != NULL);
 
  out_err:
+	if (rv && new_smi->io.io_cleanup) {
+		new_smi->io.io_cleanup(&new_smi->io);
+		new_smi->io.io_cleanup = NULL;
+	}
+
 	kfree(init_name);
 	return rv;
 }
 
 static int init_ipmi_si(void)
diff --git a/drivers/char/ipmi/ipmi_si_mem_io.c b/drivers/char/ipmi/ipmi_si_mem_io.c
index fd0ec8d6bf0e..75583612ab10 100644
--- a/drivers/char/ipmi/ipmi_si_mem_io.c
+++ b/drivers/char/ipmi/ipmi_si_mem_io.c
@@ -79,12 +79,10 @@ int ipmi_si_mem_setup(struct si_sm_io *io)
 	int           mapsize, idx;
 
 	if (!addr)
 		return -ENODEV;
 
-	io->io_cleanup = mem_cleanup;
-
 	/*
 	 * Figure out the actual readb/readw/readl/etc routine to use based
 	 * upon the register size.
 	 */
 	switch (io->regsize) {
@@ -139,7 +137,10 @@ int ipmi_si_mem_setup(struct si_sm_io *io)
 	io->addr = ioremap(addr, mapsize);
 	if (io->addr == NULL) {
 		mem_region_cleanup(io, io->io_size);
 		return -EIO;
 	}
+
+	io->io_cleanup = mem_cleanup;
+
 	return 0;
 }
diff --git a/drivers/char/ipmi/ipmi_si_port_io.c b/drivers/char/ipmi/ipmi_si_port_io.c
index ef6dffcea9fa..03924c32b6e9 100644
--- a/drivers/char/ipmi/ipmi_si_port_io.c
+++ b/drivers/char/ipmi/ipmi_si_port_io.c
@@ -66,12 +66,10 @@ int ipmi_si_port_setup(struct si_sm_io *io)
 	int          idx;
 
 	if (!addr)
 		return -ENODEV;
 
-	io->io_cleanup = port_cleanup;
-
 	/*
 	 * Figure out the actual inb/inw/inl/etc routine to use based
 	 * upon the register size.
 	 */
 	switch (io->regsize) {
@@ -107,7 +105,10 @@ int ipmi_si_port_setup(struct si_sm_io *io)
 				release_region(addr + idx * io->regspacing,
 					       io->regsize);
 			return -EIO;
 		}
 	}
+
+	io->io_cleanup = port_cleanup;
+
 	return 0;
 }

Vulnerable code: 	io->io_cleanup = mem_cleanup;

	io->io_cleanup = port_cleanup;

Fixed code: 	if (rv && new_smi->io.io_cleanup) {
		new_smi->io.io_cleanup(&new_smi->io);
		new_smi->io.io_cleanup = NULL;
	}


	io->io_cleanup = mem_cleanup;


	io->io_cleanup = port_cleanup;