Package: file
Version: 4.12-1
Severity: important
Tags: patch
I'm used to find file types of pipes, either using the output of zcat
or passing whole filesystems to stdin of file.
Since I upgraded to sarge, file tries to read the whole of stdin and
save it to a temporary file, forcing me to cut data adding a dd in the
pipe.
When inspecting the code, I found file reads the whole of the pipe
(file_pipe2file) in order to dissect ELF files, but it does it even
when the file is known not to be ELF.
By simply moving the check for ELFMAG[0123] before calling pipe2file
I recover the old behavior I loved, without loss in functionality.
Disclaimer: yes I found "-s", but it's asymettric: stdin always works.
Moreover, -s doesn't fix the problem with "bzcat <bigfile> | file -".
--- file-4.12/src/readelf.c 2004-11-24 18:38:24.000000000 +0100
+++ file-4.12-fixpipe/src/readelf.c 2005-12-28 21:55:09.000000000 +0100
@@ -751,22 +751,24 @@
int class;
int swap;
- /*
- * If we cannot seek, it must be a pipe, socket or fifo.
- */
- if((lseek(fd, (off_t)0, SEEK_SET) == (off_t)-1) && (errno == ESPIPE))
- fd = file_pipe2file(ms, fd, buf, nbytes);
+ /* Return if it's not ELF (so we avoid pipe2file unless needed) */
+ if (buf[EI_MAG0] != ELFMAG0
+ || (buf[EI_MAG1] != ELFMAG1 && buf[EI_MAG1] != OLFMAG1)
+ || buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3)
+ return 0;
/*
* ELF executables have multiple section headers in arbitrary
* file locations and thus file(1) cannot determine it from easily.
* Instead we traverse thru all section headers until a symbol table
- * one is found or else the binary is stripped.
+ * one is found or else the binary is stripped. So whole file is needed
*/
- if (buf[EI_MAG0] != ELFMAG0
- || (buf[EI_MAG1] != ELFMAG1 && buf[EI_MAG1] != OLFMAG1)
- || buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3)
- return 0;
+
+ /*
+ * If we cannot seek, it must be a pipe, socket or fifo.
+ */
+ if((lseek(fd, (off_t)0, SEEK_SET) == (off_t)-1) && (errno == ESPIPE))
+ fd = file_pipe2file(ms, fd, buf, nbytes);
class = buf[4];
--
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