Messages in this thread | | | Subject | vfs-fix-d_path-for-unreachable-paths.patch | From | Valdis.Kletnieks@vt ... | Date | Sat, 05 Sep 2009 10:22:29 -0400 |
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This patch apparently does something resembling what it's supposed to - the first few lines of /proc/mounts now looks like:
% head -5 /proc/mounts rootfs (unreachable)/ rootfs rw 0 0 /dev/root / ext3 rw,seclabel,noatime,nodiratime,user_xattr,acl,data=writeback,us rquota,grpquota 0 0 /dev /dev tmpfs rw,seclabel,relatime,mode=755 0 0 /proc /proc proc rw,relatime 0 0 /sys /sys sysfs rw,relatime 0 0
The now-unreachable rootfs is the letftover initrd rootfs.
The patch commentary notes:
> This patch addresses all these issues, by prefixing such unreachable paths > with "(unreachable)". This isn't perfect since the returned path may > still be a valid _relative_ path, and applications may not check the > result of getcwd() for starting with a '/' before using it.
It turns out that some things don't check the contents of /proc/mounts for starting with a / before using it either:
# /sbin/restorecon -v /etc/passwd Full path required for exclude: (unreachable)/.
And strace shows it's a read of /proc/mounts, not a getcwd() call:
.... open("/proc/self/task/11479/attr/current", O_RDONLY) = 3 read(3, "staff_u:sysadm_r:setfiles_t:s0\0"..., 4095) = 31 close(3) = 0 uname({sys="Linux", node="turing-police.cc.vt.edu", ...}) = 0 open("/proc/mounts", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fe 9ce36a000 read(3, "rootfs (unreachable)/ rootfs rw 0"..., 1024) = 1024 write(2, "Full path required for exclude: ("..., 48) = 48
The added "(unreachable) text also gives /etc/rc0.d/S01halt indigestion, because it thinks it can do stuff like:
awk '$2 !~ /\/(|dev|proc|selinux|sys)$/ && $1 !~ /^\/dev\/ram/ { print $2 }' \ /proc/mounts | sort -r | \ while read line; do $UMOUNT -f $line done
Somebody is buggy here, but I'm not sure who. The initrd for leaving a dangling reference, the patch for breaking /proc/mounts, or /sbin/restorecon and the shutdown script for being far too trusting of what the kernel tells it?
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