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coredump: use scoped_with_init_fs() for coredump path resolution

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Use scoped_with_init_fs() to temporarily override current->fs for
the filp_open() call so the coredump path lookup happens in init's
filesystem context. This replaces the init_root() + file_open_root()
pattern with the simpler scoped override.

coredump_file() ← do_coredump() ← vfs_coredump() ← get_signal() — runs
as the crashing userspace process

Uses init's root to prevent a chrooted/user-namespaced process from
controlling where suid coredumps land. Not a kthread, but intentionally
needs init's fs for security.

Link: https://patch.msgid.link/20260601-work-kthread-nullfs-v4-11-77ee053060e0@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Christian Brauner
2026-06-01 15:56:44 +02:00
parent f565f3b064
commit fea1107ff3
1 changed files with 3 additions and 8 deletions
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11
fs/coredump.c
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@@ -921,15 +921,10 @@ static bool coredump_file(struct core_name *cn, struct coredump_params *cprm,
* with a fully qualified path" rule is to control where
* coredumps may be placed using root privileges,
* current->fs->root must not be used. Instead, use the
* root directory of init_task.
* root directory of PID 1.
*/
struct path root;
task_lock(&init_task);
get_fs_root(init_task.fs, &root);
task_unlock(&init_task);
file = file_open_root(&root, cn->corename, open_flags, 0600);
path_put(&root);
scoped_with_init_fs()
file = filp_open(cn->corename, open_flags, 0600);
} else {
file = filp_open(cn->corename, open_flags, 0600);
}