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authorBrian Norris2022-08-26 17:44:17 -0700
committerSteven Rostedt (Google)2022-09-08 17:10:54 -0400
commit47311db8e8f33011d90dee76b39c8886120cdda4 (patch)
tree29eecd63fe2aa6f88e5bf74d3db5f817482f91f7
parent1efda38d6f9ba26ac88b359c6277f1172db03f1e (diff)
tracefs: Only clobber mode/uid/gid on remount if asked
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>
-rw-r--r--fs/tracefs/inode.c31
1 files changed, 23 insertions, 8 deletions
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 81d26abf486f..da85b3979195 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 = d_inode(sb->s_root);
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;