On Tue, 10 Feb 1998, David Schwartz wrote:
>>On Tue, 10 Feb 1998, David Schwartz wrote:
>>
>>>
>>> So? Files in the /proc directory can be transient and appear and
>>> disappear at whim.
>>Why don't the other fs's have a problem with shadows? You can make
>>ext2 files as transient as they come, and there are no shadows.
> I haven't looked closely, but my guess is that this file is for the find
>processes descriptor used to read the directory, and find's code to traverse
>a directory is sufficiently fast that a process switch rarely if ever occurs
>in between when a directory is read and the files inside it are checked.
>Therefore, only the proc entry for the find process itself is vulnerable.
Yes. This is what really happening:
[vps@phoenix]/proc$ find . -name blah -print >~/temp/a 2>&1 &
[1] 24583
[vps@phoenix]/proc$ grep -v denied ~/temp/a
find: ./24583/fd/4: No such file or directory
[1]+ Exit 1 find . -name blah -print >~/temp/a 2>&1
[vps@phoenix]/proc$
Note, pids are the same.
This is a strip from strace results ( note that strace causes to "move"
fd's) :
open(".", O_RDONLY) = 5
fcntl(5, F_SETFD, FD_CLOEXEC) = 0
close(5) = 0
open("tty", O_RDONLY) = 5
and so on. This descriptor is flying.
> In any event, this behavior is certainly not unreasonable.
If I can remember original author issued find / -name blah -print
by default , find scans the whole system ( including _all_ mounted fs's)
To avoid this one can use -xdev option.
Bye.
-- Keep cool, but don't freeze. -- Hellman's Mayonnaise
-- With best of best regards, Pawel S. Veselov (aka Black Angel) internet : vps@unicorn.niimm.spb.su ( mail,finger,talk ) Web page : http://www.niimm.spb.su/~vps/ ICQ : 5252265
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