106 lines
3.6 KiB
Diff
106 lines
3.6 KiB
Diff
From 225cb8d7473eadb481a4884e929bf23589d4bd82 Mon Sep 17 00:00:00 2001
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From: Paul Eggert <eggert@cs.ucla.edu>
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Date: Sat, 6 Apr 2024 15:13:23 -0700
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Subject: [PATCH] =?UTF-8?q?cat:=20don=E2=80=99t=20trust=20st=5Fsize=20on?=
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=?UTF-8?q?=20/proc=20files?=
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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* src/cat.c (main):
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Improve test for when copying will exhaust the output device.
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Do not rely on st_size, which is unreliable in /proc.
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Use lseek instead; this is good enough here.
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* tests/cat/cat-self.sh: Test the relaxation of the heuristic
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for self-copying.
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---
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src/cat.c | 31 +++++++++++++++++++++----------
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tests/cat/cat-self.sh | 20 ++++++++++++++++++++
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2 files changed, 41 insertions(+), 10 deletions(-)
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diff --git a/src/cat.c b/src/cat.c
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index ac39a48..14e6dfd 100644
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--- a/src/cat.c
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+++ b/src/cat.c
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@@ -646,9 +646,10 @@ main (int argc, char **argv)
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/* Optimal size of i/o operations of output. */
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idx_t outsize = io_blksize (stat_buf);
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- /* Device and I-node number of the output. */
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+ /* Device, I-node number and lazily-acquired flags of the output. */
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dev_t out_dev = stat_buf.st_dev;
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ino_t out_ino = stat_buf.st_ino;
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+ int out_flags = -2;
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/* True if the output is a regular file. */
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bool out_isreg = S_ISREG (stat_buf.st_mode) != 0;
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@@ -702,17 +703,27 @@ main (int argc, char **argv)
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fdadvise (input_desc, 0, 0, FADVISE_SEQUENTIAL);
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- /* Don't copy a nonempty regular file to itself, as that would
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- merely exhaust the output device. It's better to catch this
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- error earlier rather than later. */
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+ /* Don't copy a file to itself if that would merely exhaust the
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+ output device. It's better to catch this error earlier
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+ rather than later. */
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- if (out_isreg
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- && stat_buf.st_dev == out_dev && stat_buf.st_ino == out_ino
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- && lseek (input_desc, 0, SEEK_CUR) < stat_buf.st_size)
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+ if (stat_buf.st_dev == out_dev && stat_buf.st_ino == out_ino)
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{
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- error (0, 0, _("%s: input file is output file"), quotef (infile));
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- ok = false;
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- goto contin;
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+ if (out_flags < -1)
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+ out_flags = fcntl (STDOUT_FILENO, F_GETFL);
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+ bool exhausting = 0 <= out_flags && out_flags & O_APPEND;
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+ if (!exhausting)
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+ {
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+ off_t in_pos = lseek (input_desc, 0, SEEK_CUR);
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+ if (0 <= in_pos)
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+ exhausting = in_pos < lseek (STDOUT_FILENO, 0, SEEK_CUR);
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+ }
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+ if (exhausting)
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+ {
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+ error (0, 0, _("%s: input file is output file"), quotef (infile));
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+ ok = false;
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+ goto contin;
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+ }
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}
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/* Pointer to the input buffer. */
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diff --git a/tests/cat/cat-self.sh b/tests/cat/cat-self.sh
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index ff2afdc..f412707 100755
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--- a/tests/cat/cat-self.sh
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+++ b/tests/cat/cat-self.sh
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@@ -30,4 +30,24 @@ echo y >doc.end || framework_failure_
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cat doc doc.end >doc || fail=1
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compare doc doc.end || fail=1
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+# This terminates even though it copies a file to itself.
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+# Coreutils 9.5 and earlier rejected this.
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+echo x >fx || framework_failure_
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+echo y >fy || framework_failure_
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+cat fx fy >fxy || fail=1
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+for i in 1 2; do
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+ cat fx >fxy$i || fail=1
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+done
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+for i in 3 4 5 6; do
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+ cat fx >fx$i || fail=1
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+done
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+cat - fy <fxy1 1<>fxy1 || fail=1
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+compare fxy fxy1 || fail=1
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+cat fxy2 fy 1<>fxy2 || fail=1
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+compare fxy fxy2 || fail=1
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+returns_ 1 cat fx fx3 1<>fx3 || fail=1
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+returns_ 1 cat - fx4 <fx 1<>fx4 || fail=1
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+returns_ 1 cat fx5 >>fx5 || fail=1
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+returns_ 1 cat <fx6 >>fx6 || fail=1
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+
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Exit $fail
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--
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2.27.0
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