mtd: spi-nor: core: Prevent oops during driver removal with active read or write operations

From: kromli <[email protected]>

Ensure that the pointer passed to module_put() in spi_nor_put_device() is not NULL before use. This change adds a guard clause to return early, preventing the kernel crash below when the cadence-qspi driver is removed during a dd operation:

[  200.448732] Unable to handle kernel NULL pointer deref
erence at virtual address 0000000000000010
[  200.457576] Mem abort info:
[  200.460370]   ESR = 0x0000000096000004
[  200.464136]   EC = 0x25: DABT (current EL), IL = 32 bits
[  200.469527]   SET = 0, FnV = 0
[  200.472609]   EA = 0, S1PTW = 0
[  200.475904]   FSC = 0x04: level 0 translation fault
[  200.480786] Data abort info:
[  200.483659]   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[  200.489141]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[  200.494189]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[  200.499500] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000185df8000
[  200.505932] [0000000000000010] pgd=0000000000000000, p4d=0000000000000000
[  200.512720] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[  200.518968] Modules linked in: 8021q garp mrp stp llc bluetooth ecdh_generic
ecc rfkill crct10dif_ce rtc_ds1307 at24 stratix10_soc soc64_hwmon gpio_altera of
_fpga_region fpga_region fpga_bridge uio_pdrv_genirq uio fuse drm backlight ipv6
[  200.540016] CPU: 0 UID: 0 PID: 372 Comm: dd Not tainted 6.12.19-altera-gb6b26
c4179a6 #1
[  200.547996] Hardware name: SoCFPGA Stratix 10 SoCDK (DT)
[  200.553292] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  200.560234] pc : spi_nor_put_device+0x30/0x60
[  200.564594] lr : __put_mtd_device+0x8c/0x120
[  200.568856] sp : ffff80008411bc20
[  200.572161] x29: ffff80008411bc20 x28: ffff000185e2c500 x27: 0000000000000000
[  200.579282] x26: 0000000000000000 x25: ffff000185e2cb00 x24: ffff000185e2cc88
[  200.586404] x23: ffff00018034c620 x22: 0000000000000001 x21: ffff00018873e080
[  200.593524] x20: 0000000000000000 x19: ffff00018873e080 x18: ffffffffffffffff
[  200.600645] x17: 0030393d524f4a41 x16: 4d0064746d3d4d45 x15: ffff000185757700
[  200.607767] x14: 0000000000000000 x13: ffff000180045010 x12: ffff0001857576c0
[  200.614888] x11: 000000000000003a x10: ffff000180045018 x9 : ffff000180045010
[  200.622009] x8 : ffff80008411bb70 x7 : 0000000000000000 x6 : ffff000181325048
[  200.629129] x5 : 00000000820001cf x4 : fffffdffc60095e0 x3 : 0000000000000000
[  200.636250] x2 : 0000000000000000 x1 : ffff00018873e080 x0 : 0000000000000000
[  200.643371] Call trace:
[  200.645811]  spi_nor_put_device+0x30/0x60
[  200.649816]  __put_mtd_device+0x8c/0x120
[  200.653731]  put_mtd_device+0x30/0x48
[  200.657387]  mtdchar_close+0x30/0x78
[  200.660958]  __fput+0xc8/0x2d0
[  200.664011]  ____fput+0x14/0x20
[  200.667146]  task_work_run+0x70/0xdc
[  200.670718]  do_exit+0x2b4/0x8e4
[  200.673944]  do_group_exit+0x34/0x90
[  200.677512]  pid_child_should_wake+0x0/0x60
[  200.681686]  invoke_syscall+0x48/0x104
[  200.685432]  el0_svc_common.constprop.0+0xc0/0xe0
[  200.690128]  do_el0_svc+0x1c/0x28
[  200.693439]  el0_svc+0x30/0xcc
[  200.696454] dw_mmc ff808000.mmc: Unexpected interrupt latency
[  200.696485]  el0t_64_sync_handler+0x120/0x12c
[  200.706552]  el0t_64_sync+0x190/0x194
[  200.710213] Code: f9400000 f9417c00 f9402000 f9403400 (f9400800)
[  200.716290] ---[ end trace 0000000000000000 ]---
[  200.720948] Fixing recursive fault but reboot is needed!

---
Changes in v2:
- Move the null check prior to try_module_get().

---
 drivers/mtd/spi-nor/core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

index ac4b960101cc..4fc44455f94f 100644
@@ -3210,6 +3210,9 @@ static int spi_nor_get_device(struct mtd_info *mtd)
 	else
 		dev = nor->dev;
 
+	if (!dev && !dev->driver && !dev->driver->owner)
+		return -EINVAL;
+	
 	if (!try_module_get(dev->driver->owner))
 		return -ENODEV;
 

@@ -3227,7 +3230,8 @@ static void spi_nor_put_device(struct mtd_info *mtd)
 	else
 		dev = nor->dev;
 
-	module_put(dev->driver->owner);
+	if (dev && dev->driver && dev->driver->owner)
+		module_put(dev->driver->owner);
 }
 
 static void spi_nor_restore(struct spi_nor *nor)

2.35.3