From nobody Sun Oct 5 09:07:53 2025 Received: from mout-p-201.mailbox.org (mout-p-201.mailbox.org [80.241.56.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0B4981F09A8; Wed, 6 Aug 2025 04:48:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754455737; cv=none; b=VurPjuv3yKHfj6RY6CNqeC6ZP50HJG90dQxckq4u8xtRiVd1tXHwBS56LW3NI0KkSg6uAfZ7b1ZCYGUY4rSfzj4bSTrzcC+DnohHmVSGT1NFUX+9pHs3a3u4v7uwaMvdS23Qb1g5gWbgkB/7osP7b0EwbeTafaGY/yxXwph0bXs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754455737; c=relaxed/simple; bh=4s8Gi1EenOHJaLb55g1juwsl7ZsPZjgWY4gDBSu2WAI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Nijj9GrOueCcGpbnz6PHrtsd9vhiuotvgCNregrfc+amQ7m/NuDPSHiMuxetJS2Wc2fkcXNPmazHK/OJe72EBLpbUvd5LzvVKqaxdnfSqPyLa7O4Vfub0XTjpbTSZpZ/Cxs274VuzxzZfJ2s2XS6FqbtPejUMqX8NBC+DaYAl44= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com; spf=pass smtp.mailfrom=cyphar.com; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b=DK6PjxR/; arc=none smtp.client-ip=80.241.56.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cyphar.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b="DK6PjxR/" Received: from smtp1.mailbox.org (smtp1.mailbox.org [10.196.197.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-201.mailbox.org (Postfix) with ESMTPS id 4bxd9J21lsz9tcW; Wed, 6 Aug 2025 06:48:52 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1754455732; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yOE9waL0ew+X+ln2ytNi3KfwfeUFVHt9mFZ0tGiHb8c=; b=DK6PjxR/9ImS0JWNd3vv8Ze6rOf4pQNc/2QZhAdFa+q3bFH969lnNbTJtZVngV3LhWABS2 80EEyJoAPfrLat25yfgKuyqOFDsGvLUloSaDKHls0FmYGT4PLaPlRB/oZQW9WFG03zRO8w Ce4YqQqWrCevQgPZeTO1u7FbF1wfVq8LMLtT7QTSB9AH7YjUC64mv29WoT5l+OKWp50rYs dOYPhh2aPC0YbF/yC6BKs2SCYdY5GYS8sXrxZ3A/PiBVGujQAT/bl0PMpf23ntMrTHqQ2u C+IAwJhidXDDCcXyQc1sCLlKmDL7wwzDIOi5a9cWx4eASxE+O/p/a0dDaNetGQ== From: Aleksa Sarai Date: Wed, 06 Aug 2025 14:48:29 +1000 Subject: [PATCH 1/2] fscontext: add custom-prefix log helpers 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="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250806-errorfc-mount-too-revealing-v1-1-536540f51560@cyphar.com> References: <20250806-errorfc-mount-too-revealing-v1-0-536540f51560@cyphar.com> In-Reply-To: <20250806-errorfc-mount-too-revealing-v1-0-536540f51560@cyphar.com> To: Alexander Viro , Christian Brauner , Jan Kara Cc: David Howells , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Aleksa Sarai X-Developer-Signature: v=1; a=openpgp-sha256; l=3383; i=cyphar@cyphar.com; h=from:subject:message-id; bh=4s8Gi1EenOHJaLb55g1juwsl7ZsPZjgWY4gDBSu2WAI=; b=owGbwMvMwCWmMf3Xpe0vXfIZT6slMWRMurcqbMnxaRq538u4Ptok++s3JBy8dXzjsfkv7LV2v DqVpWdm11HKwiDGxSArpsiyzc8zdNP8xVeSP61kg5nDygQyhIGLUwAmcuM4wz+7qU/nMKxc4aIx edE8+95L9h7TMj66HRGYbHSxwYUt6aQswx9eH+WT3pu0Ln/Y8MZZ2aPoxBad5xmbug/rmdXfuKL a8YALAA== X-Developer-Key: i=cyphar@cyphar.com; a=openpgp; fpr=C9C370B246B09F6DBCFC744C34401015D1D2D386 Sometimes, errors associated with an fscontext come from the VFS or otherwise outside of the filesystem driver itself. However, the default logging of errorfc will always prefix the message with the filesystem name. So, add some *fcp() wrappers that allow for custom prefixes to be used when emitting information to the fscontext log. Signed-off-by: Aleksa Sarai --- include/linux/fs_context.h | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index 7773eb870039..671f031be173 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -186,10 +186,12 @@ struct fc_log { extern __attribute__((format(printf, 4, 5))) void logfc(struct fc_log *log, const char *prefix, char level, const char = *fmt, ...); =20 -#define __logfc(fc, l, fmt, ...) logfc((fc)->log.log, NULL, \ - l, fmt, ## __VA_ARGS__) -#define __plog(p, l, fmt, ...) logfc((p)->log, (p)->prefix, \ - l, fmt, ## __VA_ARGS__) +#define __logfc(fc, l, fmt, ...) \ + logfc((fc)->log.log, NULL, (l), (fmt), ## __VA_ARGS__) +#define __plogp(p, prefix, l, fmt, ...) \ + logfc((p)->log, (prefix), (l), (fmt), ## __VA_ARGS__) +#define __plog(p, l, fmt, ...) __plogp(p, (p)->prefix, l, fmt, ## __VA_ARG= S__) + /** * infof - Store supplementary informational message * @fc: The context in which to log the informational message @@ -201,6 +203,8 @@ void logfc(struct fc_log *log, const char *prefix, char= level, const char *fmt, #define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__) #define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__) #define infofc(fc, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__) +#define infofcp(fc, prefix, fmt, ...) \ + __plogp((&(fc)->log), prefix, 'i', fmt, ## __VA_ARGS__) =20 /** * warnf - Store supplementary warning message @@ -213,6 +217,8 @@ void logfc(struct fc_log *log, const char *prefix, char= level, const char *fmt, #define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__) #define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__) #define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__) +#define warnfcp(fc, prefix, fmt, ...) \ + __plogp((&(fc)->log), prefix, 'w', fmt, ## __VA_ARGS__) =20 /** * errorf - Store supplementary error message @@ -225,6 +231,8 @@ void logfc(struct fc_log *log, const char *prefix, char= level, const char *fmt, #define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__) #define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__) #define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS_= _) +#define errorfcp(fc, prefix, fmt, ...) \ + __plogp((&(fc)->log), prefix, 'e', fmt, ## __VA_ARGS__) =20 /** * invalf - Store supplementary invalid argument error message @@ -237,5 +245,7 @@ void logfc(struct fc_log *log, const char *prefix, char= level, const char *fmt, #define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL) #define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINV= AL) #define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL) +#define invalfcp(fc, prefix, fmt, ...) \ + (errorfcp(fc, prefix, fmt, ## __VA_ARGS__), -EINVAL) =20 #endif /* _LINUX_FS_CONTEXT_H */ --=20 2.50.1 From nobody Sun Oct 5 09:07:53 2025 Received: from mout-p-101.mailbox.org (mout-p-101.mailbox.org [80.241.56.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 973831F4CBC; Wed, 6 Aug 2025 04:48:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.151 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754455741; cv=none; b=XGLNYwHSdYvFLl+lcGvHlh0q90Gc4F4xZaw0s5YFNbJq9elJJozE5UHIUBXfjLvoSXdTzwTkDvVE953mYIYpSaFIWIhB1wqauYg/dU3BN/SVmh61fj3+6rJZ8iibs/3Ng3xDXlXpNiDtLJqyp2ZF2IG4NGEz3At6vghc1bPyvBY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754455741; c=relaxed/simple; bh=hE1jzhCIqDyIWqjL9YCdSp48W9E82NKQr3N/AJyoveA=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=rMtQ/bpVsAS1FF7AiyK4Vn9yx5gTI/ghkGKo8kJcr56GRPU2msPBc6ERg6J+tQT5CCki0MbVfIZmxyJvQ2L1wwfhrxXtAuHqzmTsBzlScTRhqQd9MtUDkDWVa+EHIWqy1pK5V0VnWuQuiC4G4yyi3ZJLkGXs+HKcKEDPTCRn7BA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com; spf=pass smtp.mailfrom=cyphar.com; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b=Vsb5mhdU; arc=none smtp.client-ip=80.241.56.151 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cyphar.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b="Vsb5mhdU" Received: from smtp1.mailbox.org (smtp1.mailbox.org [10.196.197.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-101.mailbox.org (Postfix) with ESMTPS id 4bxd9N0mCsz9tBc; Wed, 6 Aug 2025 06:48:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1754455736; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iOcmob/KBJLyEb2W1q46NfuHtAS0YPNzHthf2+pOIlc=; b=Vsb5mhdUdVEPX9SNJKEOEnQHNvxL9oBMRd+iNbJvgkhG01xY7rtkxgS+BVLBlhMHlgJSE/ sfONYwyky1IDUj8vDvU7jHojb8o9Lh4t0aiXZ6Cyja8H85MExcD8SRgbHle0T1019L6l0I aZmaE73bboQVYFUVams1dAE6ofnUP8I2wge34by98bqxGH1nh/e8qxAfBxldJQYPBXYags CNzh6B7btQciNUY/44Av+vjikDPGb5kgJCI5LNYBZn5elMN5nlsXwd50P85Qik99an0hS2 X9udLBs9SvYStfFR0W0zD3ECKYEKD+aHu6+fXogkbp270HI2Ocd8BuJfsei1Ug== From: Aleksa Sarai Date: Wed, 06 Aug 2025 14:48:30 +1000 Subject: [PATCH 2/2] vfs: output mount_too_revealing() errors to fscontext 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="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250806-errorfc-mount-too-revealing-v1-2-536540f51560@cyphar.com> References: <20250806-errorfc-mount-too-revealing-v1-0-536540f51560@cyphar.com> In-Reply-To: <20250806-errorfc-mount-too-revealing-v1-0-536540f51560@cyphar.com> To: Alexander Viro , Christian Brauner , Jan Kara Cc: David Howells , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Aleksa Sarai X-Developer-Signature: v=1; a=openpgp-sha256; l=1639; i=cyphar@cyphar.com; h=from:subject:message-id; bh=hE1jzhCIqDyIWqjL9YCdSp48W9E82NKQr3N/AJyoveA=; b=owGbwMvMwCWmMf3Xpe0vXfIZT6slMWRMurdqu8mTilSu2XnRAn46Wkv11ng98lwunXTgR4uf5 YrwgN07OkpZGMS4GGTFFFm2+XmGbpq/+Eryp5VsMHNYmUCGMHBxCsBEmKMZ/pfsad/37aH/j/J7 Mn1drm8ZNwTdKj0WNC/l6hR2YZ/MV1cZ/kqlf1P/x9FsENJq/Pb5bWdXQ5lVPc1/F5zwfWBlGx6 zgQkA X-Developer-Key: i=cyphar@cyphar.com; a=openpgp; fpr=C9C370B246B09F6DBCFC744C34401015D1D2D386 It makes little sense for fsmount() to output the warning message when mount_too_revealing() is violated to kmsg. Instead, the warning should be output (with a "VFS" prefix) to the fscontext log. In addition, include the same log message for mount_too_revealing() when doing a regular mount for consistency. With the newest fsopen()-based mount(8) from util-linux, the error messages now look like # mount -t proc proc /tmp mount: /tmp: fsmount() failed: VFS: Mount too revealing. dmesg(1) may have more information after failed mount system call. which could finally result in mount_too_revealing() errors being easier for users to detect and understand. Signed-off-by: Aleksa Sarai --- fs/namespace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 55f28cebbe7d..b2146857cbbd 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3820,8 +3820,10 @@ static int do_new_mount_fc(struct fs_context *fc, st= ruct path *mountpoint, int error; =20 error =3D security_sb_kern_mount(sb); - if (!error && mount_too_revealing(sb, &mnt_flags)) + if (!error && mount_too_revealing(sb, &mnt_flags)) { error =3D -EPERM; + errorfcp(fc, "VFS", "Mount too revealing"); + } =20 if (unlikely(error)) { fc_drop_locked(fc); @@ -4547,7 +4549,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, fl= ags, =20 ret =3D -EPERM; if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { - pr_warn("VFS: Mount too revealing\n"); + errorfcp(fc, "VFS", "Mount too revealing"); goto err_unlock; } =20 --=20 2.50.1