Package: file
Version: 4.26-2
Severity: normal
file normally does sensible things with an empty file, e.g.
$ touch empty; file empty
empty: empty
$ file - < empty
/dev/stdin: empty
but produces a confusing error message if you try to feed it an empty
file via a pipe:
$ cat empty | file
/dev/stdin: no read permission
I find this difference in strace logs suggestive:
-fstat(0, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
+fstat(0, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
read(0, ""..., 98304) = 0
+access(NULL, W_OK) = -1 EFAULT (Bad address)
+access(NULL, X_OK) = -1 EFAULT (Bad address)
-write(1, "/dev/stdin: empty\n"..., 18) = 18
+write(1, "/dev/stdin: no read permission\n"..., 31) = 31
I don't know what file is trying to do here (and I note that it is
almost always wrong to use access()), but perhaps it is assuming that a
failure of access() must be because of a lack of permissions, ignoring the
possibility of a bad pointer ... I see it call access() with a sensible
pathname if I try to use it on /etc/shadow from an unprivileged account;
this also seems wrong -- it should take the EACCES result from the open()
as authoritative -- but that might give some clues where things are going
wrong in the code.
-- System Information:
Debian Release: 5.0
APT prefers unstable
APT policy: (990, 'unstable'), (500, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.26-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
Versions of packages file depends on:
ii libc6 2.7-16 GNU C Library: Shared libraries
ii libmagic1 4.26-2 File type determination library us
ii zlib1g 1:1.2.3.3.dfsg-12 compression library - runtime
file recommends no packages.
file suggests no packages.
-- no debconf information
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