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From: Miklos Szeredi <mszeredi@redhat.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Subject: [PATCH 05/12] f*xattr: allow O_PATH descriptors
Date: Tue,  5 May 2020 11:59:08 +0200	[thread overview]
Message-ID: <20200505095915.11275-6-mszeredi@redhat.com> (raw)
In-Reply-To: <20200505095915.11275-1-mszeredi@redhat.com>

This allows xattr ops on symlink/special files referenced by an O_PATH
descriptor without having to play games with /proc/self/fd/NN (which
doesn't work for symlinks anyway).

This capability is the same as would be given by introducing ...at()
variants with an AT_EMPTY_PATH argument.  Looking at getattr/setattr type
syscalls, this is allowed for fstatat() and fchownat(), but not for
fchmodat() and utimensat().  What's the logic?

While this carries a minute risk of someone relying on the property of
xattr syscalls rejecting O_PATH descriptors, it saves the trouble of
introducing another set of syscalls.

Only file->f_path and file->f_inode are accessed in these functions.

Current versions return EBADF, hence easy to detect the presense of this
feature and fall back in case it's missing.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/xattr.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/xattr.c b/fs/xattr.c
index e13265e65871..7080bb4f3f14 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -495,7 +495,7 @@ SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 		const void __user *,value, size_t, size, int, flags)
 {
-	struct fd f = fdget(fd);
+	struct fd f = fdget_raw(fd);
 	int error = -EBADF;
 
 	if (!f.file)
@@ -587,7 +587,7 @@ SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 		void __user *, value, size_t, size)
 {
-	struct fd f = fdget(fd);
+	struct fd f = fdget_raw(fd);
 	ssize_t error = -EBADF;
 
 	if (!f.file)
@@ -662,7 +662,7 @@ SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 
 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 {
-	struct fd f = fdget(fd);
+	struct fd f = fdget_raw(fd);
 	ssize_t error = -EBADF;
 
 	if (!f.file)
@@ -727,7 +727,7 @@ SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 
 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 {
-	struct fd f = fdget(fd);
+	struct fd f = fdget_raw(fd);
 	int error = -EBADF;
 
 	if (!f.file)
-- 
2.21.1


  parent reply	other threads:[~2020-05-05  9:59 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05  9:59 [PATCH 00/12] vfs patch queue Miklos Szeredi
2020-05-05  9:59 ` [PATCH 01/12] vfs: allow unprivileged whiteout creation Miklos Szeredi
2020-05-13 19:12   ` Al Viro
2020-05-05  9:59 ` [PATCH 02/12] aio: fix async fsync creds Miklos Szeredi
2020-05-13 10:01   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 03/12] proc/mounts: add cursor Miklos Szeredi
2020-05-13 19:33   ` Al Viro
2020-05-05  9:59 ` [PATCH 04/12] utimensat: AT_EMPTY_PATH support Miklos Szeredi
2020-05-13 10:02   ` Christoph Hellwig
2020-05-05  9:59 ` Miklos Szeredi [this message]
2020-05-13 10:04   ` [PATCH 05/12] f*xattr: allow O_PATH descriptors Christoph Hellwig
2020-05-14  8:02     ` Miklos Szeredi
2020-05-14 13:01       ` Miklos Szeredi
2020-05-05  9:59 ` [PATCH 06/12] uapi: deprecate STATX_ALL Miklos Szeredi
2020-05-13 10:04   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 07/12] statx: don't clear STATX_ATIME on SB_RDONLY Miklos Szeredi
2020-05-13 10:04   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 08/12] statx: add mount ID Miklos Szeredi
2020-05-13 10:05   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 09/12] statx: add mount_root Miklos Szeredi
2020-05-05 14:24   ` J . Bruce Fields
2020-05-13 10:05   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 10/12] vfs: don't parse forbidden flags Miklos Szeredi
2020-05-13 10:06   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 11/12] vfs: don't parse "posixacl" option Miklos Szeredi
2020-05-13 10:07   ` Christoph Hellwig
2020-05-05  9:59 ` [PATCH 12/12] vfs: don't parse "silent" option Miklos Szeredi
2020-05-13 10:07   ` Christoph Hellwig
2020-05-13  7:45 ` [13/12 PATCH] vfs: add faccessat2 syscall Miklos Szeredi
2020-05-13 10:09   ` Christoph Hellwig
2020-05-13  7:47 ` [PATCH 00/12] vfs patch queue Miklos Szeredi
2020-05-13 19:48   ` Al Viro
2020-05-14 11:46     ` Miklos Szeredi
2020-05-14 14:55     ` Miklos Szeredi
2020-05-14 15:10       ` Al Viro

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