>Synopsis: Single arg invocation of mount does not mount symlink
to a dir
>Category: system
>Environment:
System : OpenBSD 5.2
Details : OpenBSD 5.2 (GENERIC.MP) #339: Wed Aug 1
10:13:24 MDT 2012
[1][email protected]:/usr/src/sys/arch/i386/compile/GENERIC.MP
Architecture: OpenBSD.i386
Machine : i386
>Description:
When trying to mount an fstab entry with mount point as a
symlink to a d
irectory, mount fails. mount_mfs can mount the same symlink but mount
doesn't. mount(2) and mount(8) were not clear as to whether node or dir
can be a symlink or not.
>How-To-Repeat:
# fgrep /tmp/c /etc/fstab
swap /tmp/c mfs rw,-s=20000 0 0
# ls -la /tmp
total 10
drwxrwxrwt 4 root wheel 512 Mar 8 19:10 .
drwxr-xr-x 15 root wheel 512 Mar 7 18:44 ..
drwx------ 3 root wheel 512 Mar 8 19:09 a
lrwx------ 1 root wheel 3 Mar 8 19:09 c -> a/b
drwxrwxrwt 2 root wheel 512 Mar 8 19:10 vi.recover
# mount /tmp/c
mount: can't find fstab entry for /tmp/c.
# mount_mfs -s 20000 swap /tmp/c
mount_mfs: reduced number of fragments per cylinder group from 2496 to
2472 to e
nlarge last cylinder group
# mount | fgrep tmp
mfs:3744 on /tmp type mfs (asynchronous, local, nodev, nosuid,
size=300000 512-b
locks)
mfs:3682 on /tmp/a/b type mfs (asynchronous, local, size=20000
512-blocks)
# umount /tmp/c
# mount | fgrep tmp
mfs:3744 on /tmp type mfs (asynchronous, local, nodev, nosuid,
size=300000 512-b
locks)
Ktrace output indicating realpath() converting symlink to the target
dir :
------
14227 mount CALL lstat(0xcfbc0a84,0xcfbbfdb8)
14227 mount NAMI "/tmp"
14227 mount STRU struct stat { dev=65280, ino=2, mode=drwxrwxrwt ,
nlink=4,
uid=0, gid=0, rdev=1208, atime=1362750114, mtime=1362750034.293781669,
ctime=13
62750034.293781669, size=512, blocks=2, blksize=8192, flags=0x0,
gen=0xd6d887d9
}
14227 mount RET lstat 0
14227 mount CALL lstat(0xcfbc0a84,0xcfbbfdb8)
14227 mount NAMI "/tmp/c"
ESC[7m/home/dexter/tr1.outESC[27mESC[K^MESC[KESC[HESC[JESC[H 14227
mount STRU
struct stat { dev=65280, ino=3, mode=lrwx------ , nlink=1, uid=0,
gid=0, rdev=
6434657, atime=1362749949.572503607, mtime=1362749949.572503607,
ctime=136274994
9.572503607, size=3, blocks=0, blksize=8192, flags=0x0, gen=0x9089c7ff
}
14227 mount RET lstat 0
14227 mount CALL readlink(0xcfbc0a84,0xcfbbfe28,0x3ff)
14227 mount NAMI "/tmp/c"
14227 mount RET readlink 3
14227 mount CALL lstat(0xcfbc0a84,0xcfbbfdb8)
14227 mount NAMI "/tmp/a"
14227 mount STRU struct stat { dev=65280, ino=18688,
mode=drwx------ , nlin
k=3, uid=0, gid=0, rdev=74408, atime=1362749947.002464837,
mtime=1362749942.0123
89559, ctime=1362749942.012389559, size=512, blocks=2, blksize=8192,
flags=0x0,
gen=0xfb109d74 }
14227 mount RET lstat 0
14227 mount CALL lstat(0xcfbc0a84,0xcfbbfdb8)
14227 mount NAMI "/tmp/a/b"
14227 mount STRU struct stat { dev=65280, ino=18689,
mode=drwx------ , nlin
k=2, uid=0, gid=0, rdev=74409, atime=1362749942.012389559,
mtime=1362749942.0123
89559, ctime=1362749942.012389559, size=512, blocks=2, blksize=8192,
flags=0x0,
gen=0xb5e63444 }
14227 mount RET lstat 0
14227 mount CALL stat(0x3c0006eb,0xcfbc09b8)
The target dir is then compared to the fstab entry instead of the
symlink given
in the cmd line.
>Fix:
Following patch to mount.c fixes this issue :-
*** mount.c.original Thu Mar 7 19:55:11 2013
--- mount.c Thu Mar 7 19:55:22 2013
***************
*** 233,238 ****
--- 233,239 ----
} else {
if ((fs = getfsfile(mntpath)) == NULL &&
(fs = getfsspec(mntpath)) == NULL &&
+ (fs = getfsfile(*argv)) == NULL &&
(fs = getfsspec(*argv)) == NULL)
errx(1, "can't find fstab entry for
%s.",
*argv);
# /usr/src/sbin/mount/mount /tmp/c
mount_mfs: reduced number of fragments per cylinder group from 2496 to
2472 to e
nlarge last cylinder group
# df -h /tmp/c
Filesystem Size Used Avail Capacity Mounted on
mfs:4880 9.3M 1.0K 8.8M 0% /tmp/a/b
# df -h /tmp/a/b
Filesystem Size Used Avail Capacity Mounted on
mfs:4880 9.3M 1.0K 8.8M 0% /tmp/a/b
dmesg:
OpenBSD 5.2 (GENERIC.MP) #339: Wed Aug 1 10:13:24 MDT 2012
[2][email protected]:/usr/src/sys/arch/i386/compile/GENERIC.MP
cpu0: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz ("GenuineIntel"
686-class) 2.50 GHz
cpu0:
FPU,V86,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36
,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,SBF,NXE,LONG,SSE3,PCLMUL,MW
AIT,DS-CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,SSE4.1,SSE4.2,x2APIC,POPCNT
,AES,XSAVE,AVX,LAHF
real mem = 3625263104 (3457MB)
avail mem = 3555172352 (3390MB)
mainbus0 at root
bios0 at mainbus0: AT/286+ BIOS, date 06/11/12, BIOS32 rev. 0 @
0xfc000, SMBIOS rev. 2.7 @ 0xe0840 (61 entries)
bios0: vendor LENOVO version "5FCN34WW" date 06/11/2012
bios0: LENOVO IdeaPad Z580
acpi at bios0 function 0x0 not configured
mpbios at bios0 function 0x0 not configured
pcibios0 at bios0: rev 3.0 @ 0xf0000/0x62d
pcibios0: PCI IRQ Routing Table rev 1.0 @ 0xfa710/448 (26 entries)
pcibios0: PCI Interrupt Router at 000:31:0 ("Intel 82371FB ISA" rev
0x00)
pcibios0: PCI bus #3 is the last bus
bios0: ROM list: 0xc0000/0xee00
cpu0 at mainbus0: (uniprocessor)
pci0 at mainbus0 bus 0: configuration mode 1 (bios)
pchb0 at pci0 dev 0 function 0 "Intel Core 3G Host" rev 0x09
vga1 at pci0 dev 2 function 0 "Intel HD Graphics 4000" rev 0x09
wsdisplay0 at vga1 mux 1: console (80x25, vt100 emulation)
wsdisplay0: screen 1-5 added (80x25, vt100 emulation)
intagp at vga1 not configured
"Intel 7 Series xHCI" rev 0x04 at pci0 dev 20 function 0 not configured
"Intel 7 Series MEI" rev 0x04 at pci0 dev 22 function 0 not configured
ehci0 at pci0 dev 26 function 0 "Intel 7 Series USB" rev 0x04: irq 11
usb0 at ehci0: USB revision 2.0
uhub0 at usb0 "Intel EHCI root hub" rev 2.00/1.00 addr 1
azalia0 at pci0 dev 27 function 0 "Intel 7 Series HD Audio" rev 0x04:
irq 10
azalia0: codecs: Realtek ALC269, Intel/0x2806, using Realtek ALC269
audio0 at azalia0
ppb0 at pci0 dev 28 function 0 "Intel 7 Series PCIE" rev 0xc4: irq 11
pci1 at ppb0 bus 1
ppb1 at pci0 dev 28 function 1 "Intel 7 Series PCIE" rev 0xc4: irq 10
pci2 at ppb1 bus 2
re0 at pci2 dev 0 function 0 "Realtek 8101E" rev 0x05: RTL8105E
(0x4080), irq 10, address
ukphy0 at re0 phy 7: Generic IEEE 802.3u media interface, rev. 2: OUI
0x000732, model 0x0008
ppb2 at pci0 dev 28 function 2 "Intel 7 Series PCIE" rev 0xc4: irq 7
pci3 at ppb2 bus 3
"Broadcom BCM4313" rev 0x01 at pci3 dev 0 function 0 not configured
ehci1 at pci0 dev 29 function 0 "Intel 7 Series USB" rev 0x04: irq 11
usb1 at ehci1: USB revision 2.0
uhub1 at usb1 "Intel EHCI root hub" rev 2.00/1.00 addr 1
pcib0 at pci0 dev 31 function 0 "Intel HM76 LPC" rev 0x04
ahci0 at pci0 dev 31 function 2 "Intel 7 Series AHCI" rev 0x04: irq 7,
AHCI 1.3
scsibus0 at ahci0: 32 targets
sd0 at scsibus0 targ 0 lun 0: <ATA, ST9500325AS, 0011> SCSI3 0/direct
fixed naa.5000c5005197cffa
sd0: 476940MB, 512 bytes/sector, 976773168 sectors
cd0 at scsibus0 targ 2 lun 0: <MATSHITA, DVD-RAM UJ8C1, 8.20> ATAPI
5/cdrom removable
ichiic0 at pci0 dev 31 function 3 "Intel 7 Series SMBus" rev 0x04: irq
7
iic0 at ichiic0
spdmem0 at iic0 addr 0x50: 4GB DDR3 SDRAM PC3-12800 SO-DIMM
isa0 at pcib0
isadma0 at isa0
pckbc0 at isa0 port 0x60/5
pckbd0 at pckbc0 (kbd slot)
pckbc0: using irq 1 for kbd slot
wskbd0 at pckbd0: console keyboard, using wsdisplay0
pms0 at pckbc0 (aux slot)
pckbc0: using irq 12 for aux slot
wsmouse0 at pms0 mux 0
pms0: Synaptics clickpad, firmware 8.1
pcppi0 at isa0 port 0x61
spkr0 at pcppi0
npx0 at isa0 port 0xf0/16: reported by CPUID; using exception 16
mtrr: Pentium Pro MTRR support
uhub2 at uhub0 port 1 "Intel Rate Matching Hub" rev 2.00/0.00 addr 2
uhidev0 at uhub2 port 1 configuration 1 interface 0 "Trust USB OPTICAL
MOUSE" rev 1.10/1.00 addr 3
uhidev0: iclass 3/1, 1 report id
ums0 at uhidev0 reportid 1: 3 buttons, Z dir
wsmouse1 at ums0 mux 0
ugen0 at uhub2 port 3 "Generic USB2.0-CRW" rev 2.00/39.60 addr 4
uhub3 at uhub1 port 1 "Intel Rate Matching Hub" rev 2.00/0.00 addr 2
uvideo0 at uhub3 port 3 configuration 1 interface 0
"LOEAAI011P2S01125K16466 Lenovo EasyCamera" rev 2.00/0.18 addr 3
video0 at uvideo0
ugen1 at uhub3 port 4 "Broadcom Corp BCM20702A0" rev 2.00/1.12 addr 4
vscsi0 at root
scsibus1 at vscsi0: 256 targets
softraid0 at root
scsibus2 at softraid0: 256 targets
root on sd0a (19378acd3782c.a) swap on sd0b dump on sd0b
sd0: 450306MB, 512 bytes/sector, 922226864 sectors
Cordially,
Srikant Tangirala.
References
1. mailto:[email protected]
2. mailto:[email protected]
