74 lines
2.2 KiB
Diff
74 lines
2.2 KiB
Diff
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From 65110210b75d38908cdd84cb202cf013ccf6ed0e Mon Sep 17 00:00:00 2001
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From: Greg Hudson <ghudson@mit.edu>
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Date: Sun, 14 Aug 2016 12:08:16 -0400
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Subject: [PATCH] Work around glibc OFD lock bug on 32-bit Linux
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A bug in Gnu libc causes OFD locking to fail unpredictably on 32-bit
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Linux, typically leading to deadlocks. Work around this bug by using
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the fcntl64 system call and struct flock64.
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See also: https://sourceware.org/bugzilla/show_bug.cgi?id=20251
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ticket: 8474
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target_version: 1.14-next
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tags: pullup
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---
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src/lib/krb5/os/lock_file.c | 26 ++++++++++++++++++++++++--
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1 file changed, 24 insertions(+), 2 deletions(-)
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diff --git a/src/lib/krb5/os/lock_file.c b/src/lib/krb5/os/lock_file.c
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index a2f247c..2360c96 100644
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--- a/src/lib/krb5/os/lock_file.c
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+++ b/src/lib/krb5/os/lock_file.c
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@@ -43,7 +43,29 @@
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#if defined(HAVE_FCNTL_H) && defined(F_SETLKW) && defined(F_RDLCK)
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#define POSIX_FILE_LOCKS
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+
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+/*
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+ * Gnu libc bug 20251, currently unfixed, breaks OFD lock support on
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+ * 32-bit platforms. Work around this bug by explicitly using the
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+ * fcntl64 system call and struct flock64.
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+ */
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+#if defined(__linux__) && __WORDSIZE == 32
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+#include <sys/syscall.h>
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+#ifdef SYS_fcntl64
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+#define USE_FCNTL64
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#endif
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+#endif
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+#ifdef USE_FCNTL64
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+/* Use the fcntl64 system call and struct flock64. (Gnu libc does not
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+ * define a fcntl64() function, so we must use syscall().) */
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+#define fcntl(fd, cmd, arg) syscall(SYS_fcntl64, fd, cmd, arg)
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+typedef struct flock64 fcntl_lock_st;
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+#else
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+/* Use regular fcntl() and struct flock. */
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+typedef struct flock fcntl_lock_st;
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+#endif
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+
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+#endif /* defined(HAVE_FCNTL_H) && defined(F_SETLKW) && defined(F_RDLCK) */
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#ifdef HAVE_FLOCK
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#ifndef sysvimp
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@@ -66,7 +88,7 @@
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* older kernel than we were built with.
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*/
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static int
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-ofdlock(int fd, int cmd, struct flock *lock_arg)
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+ofdlock(int fd, int cmd, fcntl_lock_st *lock_arg)
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{
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#ifdef F_OFD_SETLKW
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int st, ofdcmd;
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@@ -89,7 +111,7 @@ krb5_lock_file(krb5_context context, int fd, int mode)
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krb5_error_code retval = 0;
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#ifdef POSIX_FILE_LOCKS
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int lock_cmd = F_SETLKW;
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- struct flock lock_arg = { 0 };
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+ fcntl_lock_st lock_arg = { 0 };
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#endif
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switch (mode & ~KRB5_LOCKMODE_DONTBLOCK) {
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--
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2.8.1
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