From: Kenji Kaneshige Date: Wed, 23 Jun 2010 07:04:10 +0000 (+0900) Subject: PCI: kernel oops on access to pci proc file while hot-removal X-Git-Tag: firefly_0821_release~9833^2~1253^2~13 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8cc2bfd87fdd2f4a31f39c86f59df4b4be2c0adc;p=firefly-linux-kernel-4.4.55.git PCI: kernel oops on access to pci proc file while hot-removal I encountered the problem that /proc/bus/pci/XX/YY is not removed even after the corresponding device is hot-removed, if the file is still being opened. In addtion, accessing this file in this situation causes kernel panic (see below). Becasue the pci_proc_detach_device() doesn't call remove_proc_entry() if struct proc_dir_entry->count > 1, access to /proc/bus/pci/XX/YY would refer to struct pci_dev that was already freed. Though I don't know why the check for proc_dir_entry->count was added, I don't think it is needed. Removing this check fixes the problem. Steps to reproduce ------------------ # cd /sys/bus/pci/slots/2/ # PROC_BUS_PCI_FILE=/proc/bus/pci/`awk -F: '{print $2"/"$3}' < address`.0 # sleep 10000 < $PROC_BUS_PCI_FILE & # echo 0 > power # while true; do cat $PROC_BUS_PCI_FILE > /dev/null; done Oops Messages ------------- BUG: unable to handle kernel NULL pointer dereference at 00000042 IP: [] pci_user_read_config_dword+0x65/0xa0 *pdpt = 000000002185e001 *pde = 0000000476a79067 Oops: 0000 [#1] SMP last sysfs file: /sys/devices/pci0000:00/0000:00:1c.0/0000:10:00.0/local_cpus Modules linked in: autofs4 sunrpc cpufreq_ondemand acpi_cpufreq ipv6 dm_mirror dm_region_hash dm_log dm_mod e1000e i2c_i801 i2c_core iTCO_wdt igb sg pcspkr dca iTCO_vendor_support ext4 mbcache jbd2 sd_mod crc_t10dif lpfc mptsas scsi_transport_fc mptscsih mptbase scsi_tgt scsi_transport_sas [last unloaded: microcode] Pid: 2997, comm: cat Not tainted 2.6.34-kk #32 SB/PRIMEQUEST 1800E EIP: 0060:[] EFLAGS: 00010046 CPU: 19 EIP is at pci_user_read_config_dword+0x65/0xa0 EAX: 00000002 EBX: e44f1800 ECX: e144df14 EDX: 155668c7 ESI: 00000087 EDI: 00000000 EBP: e144df40 ESP: e144df0c DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 Process cat (pid: 2997, ti=e144c000 task=e26f2570 task.ti=e144c000) Stack: c09ceac0 c0570f72 ffffffff 08c57000 00000000 00001000 e44f1800 c05d2404 <0> e144df40 00001000 00000000 00001000 08c57000 3093ae50 e420cb40 e358d5c0 <0> c05d2300 fffffffb c054984f e144df9c 00008000 08c57000 e358d5c0 00008000 Call Trace: [] ? security_capable+0x22/0x30 [] ? proc_bus_pci_read+0x104/0x220 [] ? proc_bus_pci_read+0x0/0x220 [] ? proc_reg_read+0x5f/0x90 [] ? proc_reg_read+0x0/0x90 [] ? vfs_read+0x9d/0x190 [] ? audit_syscall_entry+0x204/0x230 [] ? sys_read+0x41/0x70 [] ? sysenter_do_call+0x12/0x28 Code: b4 26 00 00 00 00 b8 20 88 b1 c0 c7 44 24 08 ff ff ff ff e8 3e 52 22 00 f6 83 24 04 00 00 20 75 34 8b 43 08 8d 4c 24 08 8b 53 1c <8b> 70 40 89 4c 24 04 89 f9 c7 04 24 04 00 00 00 ff 16 89 c6 f0 EIP: [] pci_user_read_config_dword+0x65/0xa0 SS:ESP 0068:e144df0c CR2: 0000000000000042 Acked-by: Greg Kroah-Hartman Signed-off-by: Kenji Kaneshige Signed-off-by: Jesse Barnes --- diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c index 449e890267a2..68316b59d7d3 100644 --- a/drivers/pci/proc.c +++ b/drivers/pci/proc.c @@ -431,8 +431,6 @@ int pci_proc_detach_device(struct pci_dev *dev) struct proc_dir_entry *e; if ((e = dev->procent)) { - if (atomic_read(&e->count) > 1) - return -EBUSY; remove_proc_entry(e->name, dev->bus->procdir); dev->procent = NULL; }