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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47761c2fe2asm285284515e9.5.2025.11.10.15.11.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Nov 2025 15:11:59 -0800 (PST) Date: Mon, 10 Nov 2025 23:11:57 +0000 From: David Laight To: Masaharu Noguchi Cc: Jeff Layton , Chuck Lever , Jesper Juhl , Alexander Aring , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] uapi: fcntl: guard AT_RENAME_* aliases Message-ID: <20251110231157.4ab7601b@pumpkin> In-Reply-To: <20251110144232.3765169-2-nogunix@gmail.com> References: <20251110144232.3765169-1-nogunix@gmail.com> <20251110144232.3765169-2-nogunix@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 10 Nov 2025 23:42:31 +0900 Masaharu Noguchi wrote: > Including after libc headers such as stdio.h may leave > the renameat2() flag macros defined to libc's values. That leaks the > wrong numbers into user space even though the kernel header tries to > provide its own aliases. > > Check whether AT_RENAME_* is already defined and whether the value > matches what the uapi header expects. If not, drop the old definition > and replace it with the kernel one so the exported flags stay stable > regardless of include order. > > Signed-off-by: Masaharu Noguchi > --- > include/uapi/linux/fcntl.h | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h > index 3741ea1b73d8..8b667550e44a 100644 > --- a/include/uapi/linux/fcntl.h > +++ b/include/uapi/linux/fcntl.h > @@ -156,10 +156,23 @@ > * as possible, so we can use them for generic bits in the future if necessary. > */ > > -/* Flags for renameat2(2) (must match legacy RENAME_* flags). */ > +/* Flags for renameat2(2) (must match legacy RENAME_* flags). > + * stdio.h may define these differently, so check explicitly. > + */ > +#if !defined(AT_RENAME_NOREPLACE) || AT_RENAME_NOREPLACE != 0x0001 > +#undef AT_RENAME_NOREPLACE I deliberately left out the #undef so you'd get a compile-time error if the values of the definitions differ. David > #define AT_RENAME_NOREPLACE 0x0001 > +#endif > + > +#if !defined(AT_RENAME_EXCHANGE) || AT_RENAME_EXCHANGE != 0x0002 > +#undef AT_RENAME_EXCHANGE > #define AT_RENAME_EXCHANGE 0x0002 > +#endif > + > +#if !defined(AT_RENAME_WHITEOUT) || AT_RENAME_WHITEOUT != 0x0004 > +#undef AT_RENAME_WHITEOUT > #define AT_RENAME_WHITEOUT 0x0004 > +#endif > > /* Flag for faccessat(2). */ > #define AT_EACCESS 0x200 /* Test access permitted for