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181 lines
6.0 KiB
181 lines
6.0 KiB
From c7a04cef4075da864a3468e63a5bb79334d8f556 Mon Sep 17 00:00:00 2001 |
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From: Paul Eggert <eggert@cs.ucla.edu> |
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Date: Sat, 26 Jun 2021 18:23:52 -0700 |
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Subject: [PATCH] tail: use poll, not select |
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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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This fixes an unlikely stack out-of-bounds write reported by |
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Stepan Broz via Kamil Dudka (Bug#49209). |
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* src/tail.c: Do not include <sys/select.h>. |
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[!_AIX]: Include poll.h. |
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(check_output_alive) [!_AIX]: Use poll instead of select. |
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(tail_forever_inotify): Likewise. Simplify logic, as there is no |
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need for a ‘while (len <= evbuf_off)’ loop. |
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Upstream-commit: da0d448bca62c6305fc432f67e2c5ccc2da75346 |
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Signed-off-by: Kamil Dudka <kdudka@redhat.com> |
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--- |
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src/tail.c | 100 +++++++++++++++++++++-------------------------------- |
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1 file changed, 39 insertions(+), 61 deletions(-) |
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diff --git a/src/tail.c b/src/tail.c |
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index 1c88723..5b4f21a 100644 |
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--- a/src/tail.c |
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+++ b/src/tail.c |
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@@ -28,12 +28,9 @@ |
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#include <stdio.h> |
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#include <assert.h> |
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#include <getopt.h> |
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-#include <sys/select.h> |
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+#include <poll.h> |
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#include <sys/types.h> |
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#include <signal.h> |
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-#ifdef _AIX |
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-# include <poll.h> |
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-#endif |
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#include "system.h" |
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#include "argmatch.h" |
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@@ -351,27 +348,12 @@ check_output_alive (void) |
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if (! monitor_output) |
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return; |
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-#ifdef _AIX |
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- /* select on AIX was seen to give a readable event immediately. */ |
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struct pollfd pfd; |
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pfd.fd = STDOUT_FILENO; |
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pfd.events = POLLERR; |
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if (poll (&pfd, 1, 0) >= 0 && (pfd.revents & POLLERR)) |
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die_pipe (); |
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-#else |
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- struct timeval delay; |
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- delay.tv_sec = delay.tv_usec = 0; |
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- |
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- fd_set rfd; |
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- FD_ZERO (&rfd); |
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- FD_SET (STDOUT_FILENO, &rfd); |
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- |
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- /* readable event on STDOUT is equivalent to POLLERR, |
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- and implies an error condition on output like broken pipe. */ |
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- if (select (STDOUT_FILENO + 1, &rfd, NULL, NULL, &delay) == 1) |
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- die_pipe (); |
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-#endif |
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} |
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static bool |
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@@ -1612,7 +1594,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, |
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/* Wait for inotify events and handle them. Events on directories |
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ensure that watched files can be re-added when following by name. |
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This loop blocks on the 'safe_read' call until a new event is notified. |
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- But when --pid=P is specified, tail usually waits via the select. */ |
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+ But when --pid=P is specified, tail usually waits via poll. */ |
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while (1) |
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{ |
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struct File_spec *fspec; |
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@@ -1629,54 +1611,51 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, |
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return false; |
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} |
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- /* When watching a PID, ensure that a read from WD will not block |
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- indefinitely. */ |
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- while (len <= evbuf_off) |
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+ if (len <= evbuf_off) |
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{ |
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- struct timeval delay; /* how long to wait for file changes. */ |
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+ /* Poll for inotify events. When watching a PID, ensure |
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+ that a read from WD will not block indefinitely. |
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+ If MONITOR_OUTPUT, also poll for a broken output pipe. */ |
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- if (pid) |
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+ int file_change; |
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+ struct pollfd pfd[2]; |
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+ do |
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{ |
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- if (writer_is_dead) |
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- exit (EXIT_SUCCESS); |
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+ /* How many ms to wait for changes. -1 means wait forever. */ |
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+ int delay = -1; |
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- writer_is_dead = (kill (pid, 0) != 0 && errno != EPERM); |
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- |
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- if (writer_is_dead) |
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- delay.tv_sec = delay.tv_usec = 0; |
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- else |
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+ if (pid) |
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{ |
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- delay.tv_sec = (time_t) sleep_interval; |
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- delay.tv_usec = 1000000 * (sleep_interval - delay.tv_sec); |
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+ if (writer_is_dead) |
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+ exit (EXIT_SUCCESS); |
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+ |
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+ writer_is_dead = (kill (pid, 0) != 0 && errno != EPERM); |
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+ |
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+ if (writer_is_dead || sleep_interval <= 0) |
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+ delay = 0; |
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+ else if (sleep_interval < INT_MAX / 1000 - 1) |
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+ { |
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+ /* delay = ceil (sleep_interval * 1000), sans libm. */ |
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+ double ddelay = sleep_interval * 1000; |
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+ delay = ddelay; |
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+ delay += delay < ddelay; |
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+ } |
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} |
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+ |
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+ pfd[0].fd = wd; |
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+ pfd[0].events = POLLIN; |
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+ pfd[1].fd = STDOUT_FILENO; |
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+ pfd[1].events = pfd[1].revents = 0; |
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+ file_change = poll (pfd, monitor_output + 1, delay); |
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} |
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+ while (file_change == 0); |
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- fd_set rfd; |
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- FD_ZERO (&rfd); |
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- FD_SET (wd, &rfd); |
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- if (monitor_output) |
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- FD_SET (STDOUT_FILENO, &rfd); |
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- |
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- int file_change = select (MAX (wd, STDOUT_FILENO) + 1, |
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- &rfd, NULL, NULL, pid ? &delay: NULL); |
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- |
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- if (file_change == 0) |
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- continue; |
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- else if (file_change == -1) |
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- die (EXIT_FAILURE, errno, |
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- _("error waiting for inotify and output events")); |
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- else if (FD_ISSET (STDOUT_FILENO, &rfd)) |
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- { |
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- /* readable event on STDOUT is equivalent to POLLERR, |
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- and implies an error on output like broken pipe. */ |
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- die_pipe (); |
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- } |
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- else |
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- break; |
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- } |
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+ if (file_change < 0) |
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+ die (EXIT_FAILURE, errno, |
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+ _("error waiting for inotify and output events")); |
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+ if (pfd[1].revents) |
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+ die_pipe (); |
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- if (len <= evbuf_off) |
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- { |
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len = safe_read (wd, evbuf, evlen); |
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evbuf_off = 0; |
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@@ -2437,8 +2416,7 @@ main (int argc, char **argv) |
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if (forever && ignore_fifo_and_pipe (F, n_files)) |
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{ |
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/* If stdout is a fifo or pipe, then monitor it |
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- so that we exit if the reader goes away. |
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- Note select() on a regular file is always readable. */ |
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+ so that we exit if the reader goes away. */ |
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struct stat out_stat; |
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if (fstat (STDOUT_FILENO, &out_stat) < 0) |
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die (EXIT_FAILURE, errno, _("standard output")); |
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-- |
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2.31.1 |
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