From b15e501f036cb8a4228c403bc84b88f5dbb81ef1 Mon Sep 17 00:00:00 2001
From: Brian Norris <briannorris@chromium.org>
Date: Tue, 11 Oct 2022 12:14:20 +0000
Subject: [PATCH] tracefs: Only clobber mode/uid/gid on remount if asked
stable inclusion
from stable-v4.19.259
commit 27591187f95e6f67a40bba46f8306699d2ecbd81
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5V45M
CVE: NA
---------------------------
[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
---
fs/tracefs/inode.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index f4ea7bf13386..ae0a660b98b6 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -142,6 +142,8 @@ struct tracefs_mount_opts {
kuid_t uid;
kgid_t gid;
umode_t mode;
+ /* Opt_* bitfield. */
+ unsigned int opts;
};
enum {
@@ -171,6 +173,7 @@ 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) {
@@ -205,22 +208,34 @@ 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;
+ }
+
+ if (!remount || opts->opts & BIT(Opt_uid))
+ inode->i_uid = opts->uid;
- inode->i_uid = opts->uid;
- inode->i_gid = opts->gid;
+ if (!remount || opts->opts & BIT(Opt_gid))
+ inode->i_gid = opts->gid;
return 0;
}
@@ -235,7 +250,7 @@ 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;
@@ -287,7 +302,7 @@ 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;
--
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