From 6c6ce2d0c3cb7365c7ebe3457bcbc0e3874fe600 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 11 Jun 2025 17:13:34 -0700 Subject: [PATCH] fuse2fs: allow O_APPEND and O_TRUNC opens Commit 9f69dfc4e275cc didn't quite get the permissions checking correct: generic/362 - output mismatch (see /var/tmp/fstests/generic/362.out.bad) --- tests/generic/362.out 2025-04-30 16:20:44.563833050 -0700 +++ /var/tmp/fstests/generic/362.out.bad 2025-06-11 17:04:24.061193618 -0700 @@ -1,2 +1,3 @@ QA output created by 362 +Failed to open/create file: Operation not permitted Silence is golden ... (Run 'diff -u /run/fstests/bin/tests/generic/362.out /var/tmp/fstests/generic/362.out.bad' to see the entire diff) The kernel allows opening a file for append and truncation. What it doesn't allow is opening an append-only file for truncation. Note that this causes generic/079 to regress, but the root cause of that problem is actually that fuse oddly supports FS_IOC_[GS]ETFLAGS but doesn't actually set the VFS inode flags. Cc: # v1.47.3 Fixes: 9f69dfc4e275cc ("fuse2fs: implement O_APPEND correctly") Signed-off-by: "Darrick J. Wong" --- misc/fuse2fs.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c index cce1c97c..1debbd33 100644 --- a/misc/fuse2fs.c +++ b/misc/fuse2fs.c @@ -2639,15 +2639,13 @@ static int __op_open(struct fuse2fs *ff, const char *path, file->open_flags |= EXT2_FILE_WRITE; break; } - if (fp->flags & O_APPEND) { - /* the kernel doesn't allow truncation of an append-only file */ - if (fp->flags & O_TRUNC) { - ret = -EPERM; - goto out; - } + /* + * If the caller wants to truncate the file, we need to ask for full + * write access even if the caller claims to be appending. + */ + if ((fp->flags & O_APPEND) && !(fp->flags & O_TRUNC)) check |= A_OK; - } detect_linux_executable_open(fp->flags, &check, &file->open_flags); -- 2.47.3