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commit    ced0cdc76cfc09eaa722e79fe9720729703da2ce
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Mon May 21 04:32:28 2018 +0000
First released in: 11.0, 9.4.19, 9.5.14, 9.6.10, 10.5

    Fix unsafe usage of strerror(errno) within ereport().
    
    This is the converse of the unsafe-usage-of-%m problem: the reason
    ereport/elog provide that format code is mainly to dodge the hazard
    of errno getting changed before control reaches functions within the
    arguments of the macro.  I only found one instance of this hazard,
    but it's been there since 9.4 :-(.


 src/backend/libpq/auth.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index 8fb518dbc24..c3339b0ce76 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -1620,10 +1620,12 @@ auth_peer(hbaPort *port)
 	pw = getpwuid(uid);
 	if (!pw)
 	{
+		int			save_errno = errno;
+
 		ereport(LOG,
 				(errmsg("could not look up local user ID %ld: %s",
 						(long) uid,
-						errno ? strerror(errno) : _("user does not exist"))));
+						save_errno ? strerror(save_errno) : _("user does not exist"))));
 		return STATUS_ERROR;
 	}
 


[parent: 29a4db65fbb7]