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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Brian Norris <briannorris@chromium.org>,
	"Steven Rostedt (Google)" <rostedt@goodmis.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 11/35] tracefs: Only clobber mode/uid/gid on remount if asked
Date: Fri, 16 Sep 2022 12:08:34 +0200	[thread overview]
Message-ID: <20220916100447.413009805@linuxfoundation.org> (raw)
In-Reply-To: <20220916100446.916515275@linuxfoundation.org>

From: Brian Norris <briannorris@chromium.org>

[ Upstream commit 47311db8e8f33011d90dee76b39c8886120cdda4 ]

Users may have explicitly configured their tracefs permissions; we
shouldn't overwrite those just because a second mount appeared.

Only clobber if the options were provided at mount time.

Note: the previous behavior was especially surprising in the presence of
automounted /sys/kernel/debug/tracing/.

Existing behavior:

  ## Pre-existing status: tracefs is 0755.
  # stat -c '%A' /sys/kernel/tracing/
  drwxr-xr-x

  ## (Re)trigger the automount.
  # umount /sys/kernel/debug/tracing
  # stat -c '%A' /sys/kernel/debug/tracing/.
  drwx------

  ## Unexpected: the automount changed mode for other mount instances.
  # stat -c '%A' /sys/kernel/tracing/
  drwx------

New behavior (after this change):

  ## Pre-existing status: tracefs is 0755.
  # stat -c '%A' /sys/kernel/tracing/
  drwxr-xr-x

  ## (Re)trigger the automount.
  # umount /sys/kernel/debug/tracing
  # stat -c '%A' /sys/kernel/debug/tracing/.
  drwxr-xr-x

  ## Expected: the automount does not change other mount instances.
  # stat -c '%A' /sys/kernel/tracing/
  drwxr-xr-x

Link: https://lkml.kernel.org/r/20220826174353.2.Iab6e5ea57963d6deca5311b27fb7226790d44406@changeid

Cc: stable@vger.kernel.org
Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/tracefs/inode.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index f2625a372a3ae..066e8344934de 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -141,6 +141,8 @@ struct tracefs_mount_opts {
 	kuid_t uid;
 	kgid_t gid;
 	umode_t mode;
+	/* Opt_* bitfield. */
+	unsigned int opts;
 };
 
 enum {
@@ -241,6 +243,7 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 	kgid_t gid;
 	char *p;
 
+	opts->opts = 0;
 	opts->mode = TRACEFS_DEFAULT_MODE;
 
 	while ((p = strsep(&data, ",")) != NULL) {
@@ -275,24 +278,36 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 		 * but traditionally tracefs has ignored all mount options
 		 */
 		}
+
+		opts->opts |= BIT(token);
 	}
 
 	return 0;
 }
 
-static int tracefs_apply_options(struct super_block *sb)
+static int tracefs_apply_options(struct super_block *sb, bool remount)
 {
 	struct tracefs_fs_info *fsi = sb->s_fs_info;
 	struct inode *inode = sb->s_root->d_inode;
 	struct tracefs_mount_opts *opts = &fsi->mount_opts;
 
-	inode->i_mode &= ~S_IALLUGO;
-	inode->i_mode |= opts->mode;
+	/*
+	 * On remount, only reset mode/uid/gid if they were provided as mount
+	 * options.
+	 */
+
+	if (!remount || opts->opts & BIT(Opt_mode)) {
+		inode->i_mode &= ~S_IALLUGO;
+		inode->i_mode |= opts->mode;
+	}
 
-	inode->i_uid = opts->uid;
+	if (!remount || opts->opts & BIT(Opt_uid))
+		inode->i_uid = opts->uid;
 
-	/* Set all the group ids to the mount option */
-	set_gid(sb->s_root, opts->gid);
+	if (!remount || opts->opts & BIT(Opt_gid)) {
+		/* Set all the group ids to the mount option */
+		set_gid(sb->s_root, opts->gid);
+	}
 
 	return 0;
 }
@@ -307,7 +322,7 @@ static int tracefs_remount(struct super_block *sb, int *flags, char *data)
 	if (err)
 		goto fail;
 
-	tracefs_apply_options(sb);
+	tracefs_apply_options(sb, true);
 
 fail:
 	return err;
@@ -359,7 +374,7 @@ static int trace_fill_super(struct super_block *sb, void *data, int silent)
 
 	sb->s_op = &tracefs_super_operations;
 
-	tracefs_apply_options(sb);
+	tracefs_apply_options(sb, false);
 
 	return 0;
 
-- 
2.35.1




  parent reply	other threads:[~2022-09-16 10:18 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-16 10:08 [PATCH 5.15 00/35] 5.15.69-rc1 review Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 01/35] NFS: Fix WARN_ON due to unionization of nfs_inode.nrequests Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 02/35] ACPI: resource: skip IRQ override on AMD Zen platforms Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 03/35] ARM: dts: imx: align SPI NOR node name with dtschema Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 04/35] ARM: dts: imx6qdl-kontron-samx6i: fix spi-flash compatible Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 05/35] ARM: dts: at91: fix low limit for CPU regulator Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 06/35] ARM: dts: at91: sama7g5ek: specify proper regulator output ranges Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 07/35] lockdep: Fix -Wunused-parameter for _THIS_IP_ Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 08/35] x86/mm: Force-inline __phys_addr_nodebug() Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 09/35] task_stack, x86/cea: Force-inline stack helpers Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 10/35] tracing: hold caller_addr to hardirq_{enable,disable}_ip Greg Kroah-Hartman
2022-09-16 10:08 ` Greg Kroah-Hartman [this message]
2022-09-16 10:08 ` [PATCH 5.15 12/35] iommu/vt-d: Fix kdump kernels boot failure with scalable mode Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 13/35] Input: goodix - add support for GT1158 Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 14/35] platform/surface: aggregator_registry: Add support for Surface Laptop Go 2 Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 15/35] drm/msm/rd: Fix FIFO-full deadlock Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 16/35] hwmon: (pmbus) Use dev_err_probe() to filter -EPROBE_DEFER error messages Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 17/35] dt-bindings: iio: gyroscope: bosch,bmg160: correct number of pins Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 18/35] HID: ishtp-hid-clientHID: ishtp-hid-client: Fix comment typo Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 19/35] hid: intel-ish-hid: ishtp: Fix ishtp client sending disordered message Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 20/35] tg3: Disable tg3 device on system reboot to avoid triggering AER Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 21/35] gpio: mockup: remove gpio debugfs when remove device Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 22/35] ieee802154: cc2520: add rc code in cc2520_tx() Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 23/35] Input: iforce - add support for Boeder Force Feedback Wheel Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 24/35] nvmet-tcp: fix unhandled tcp states in nvmet_tcp_state_change() Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 25/35] drm/amd/amdgpu: skip ucode loading if ucode_size == 0 Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 26/35] net: dsa: hellcreek: Print warning only once Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 27/35] perf/arm_pmu_platform: fix tests for platform_get_irq() failure Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 28/35] platform/x86: acer-wmi: Acer Aspire One AOD270/Packard Bell Dot keymap fixes Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 29/35] usb: storage: Add ASUS <0x0b05:0x1932> to IGNORE_UAS Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 30/35] mm: Fix TLB flush for not-first PFNMAP mappings in unmap_region() Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 31/35] soc: fsl: select FSL_GUTS driver for DPIO Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 32/35] usb: gadget: f_uac2: clean up some inconsistent indenting Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 33/35] usb: gadget: f_uac2: fix superspeed transfer Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 34/35] RDMA/irdma: Use s/g array in post send only when its valid Greg Kroah-Hartman
2022-09-16 10:08 ` [PATCH 5.15 35/35] Input: goodix - add compatible string for GT1158 Greg Kroah-Hartman
2022-09-16 21:48 ` [PATCH 5.15 00/35] 5.15.69-rc1 review Guenter Roeck
2022-09-17  4:11 ` Bagas Sanjaya
2022-09-17 10:19 ` Ron Economos
2022-09-17 14:09 ` Sudip Mukherjee (Codethink)
2022-09-17 15:57 ` Naresh Kamboju
2022-09-19  0:00 ` Florian Fainelli

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