From 2cf70fa676bacf97c24fd0b80bab6fec06b9f2db Mon Sep 17 00:00:00 2001 From: Michael Banck Date: Tue, 10 Jun 2025 12:23:17 +0200 Subject: [PATCH 1/2] Make safeguard against incorrect fd flags for fsync more portable. The current code assumed that O_RDONLY is defined as 0, but this is not universally the case. To fix this, mask the flags with O_ACCMODE and assert that they are O_RDONLY for directories or not O_RDONLY for files. Co-authored-by: Samuel Thibault --- src/backend/storage/file/fd.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c index 0e8299dd556..cd1e661974a 100644 --- a/src/backend/storage/file/fd.c +++ b/src/backend/storage/file/fd.c @@ -411,14 +411,12 @@ pg_fsync(int fd) { int desc_flags = fcntl(fd, F_GETFL); - /* - * O_RDONLY is historically 0, so just make sure that for directories - * no write flags are used. - */ + desc_flags &= O_ACCMODE; + if (S_ISDIR(st.st_mode)) - Assert((desc_flags & (O_RDWR | O_WRONLY)) == 0); + Assert(desc_flags == O_RDONLY); else - Assert((desc_flags & (O_RDWR | O_WRONLY)) != 0); + Assert(desc_flags != O_RDONLY); } errno = 0; #endif -- 2.39.5