Merge tag 'vfs-6.17-rc1.coredump' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull coredump updates from Christian Brauner:
 "This contains an extension to the coredump socket and a proper rework
  of the coredump code.

   - This extends the coredump socket to allow the coredump server to
     tell the kernel how to process individual coredumps. This allows
     for fine-grained coredump management. Userspace can decide to just
     let the kernel write out the coredump, or generate the coredump
     itself, or just reject it.

     * COREDUMP_KERNEL
       The kernel will write the coredump data to the socket.

     * COREDUMP_USERSPACE
       The kernel will not write coredump data but will indicate to the
       parent that a coredump has been generated. This is used when
       userspace generates its own coredumps.

     * COREDUMP_REJECT
       The kernel will skip generating a coredump for this task.

     * COREDUMP_WAIT
       The kernel will prevent the task from exiting until the coredump
       server has shutdown the socket connection.

     The flexible coredump socket can be enabled by using the "@@"
     prefix instead of the single "@" prefix for the regular coredump
     socket:

       @@/run/systemd/coredump.socket

   - Cleanup the coredump code properly while we have to touch it
     anyway.

     Split out each coredump mode in a separate helper so it's easy to
     grasp what is going on and make the code easier to follow. The core
     coredump function should now be very trivial to follow"

* tag 'vfs-6.17-rc1.coredump' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (31 commits)
  cleanup: add a scoped version of CLASS()
  coredump: add coredump_skip() helper
  coredump: avoid pointless variable
  coredump: order auto cleanup variables at the top
  coredump: add coredump_cleanup()
  coredump: auto cleanup prepare_creds()
  cred: add auto cleanup method
  coredump: directly return
  coredump: auto cleanup argv
  coredump: add coredump_write()
  coredump: use a single helper for the socket
  coredump: move pipe specific file check into coredump_pipe()
  coredump: split pipe coredumping into coredump_pipe()
  coredump: move core_pipe_count to global variable
  coredump: prepare to simplify exit paths
  coredump: split file coredumping into coredump_file()
  coredump: rename do_coredump() to vfs_coredump()
  selftests/coredump: make sure invalid paths are rejected
  coredump: validate socket path in coredump_parse()
  coredump: don't allow ".." in coredump socket path
  ...

5 files changed, 132 insertions, 2 deletions

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 7093e1d08af0..bee606bebaca 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -277,6 +277,14 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 	class_##_name##_t var __cleanup(class_##_name##_destructor) =	\
 		class_##_name##_constructor
 
+#define scoped_class(_name, var, args)                          \
+	for (CLASS(_name, var)(args);                           \
+	     __guard_ptr(_name)(&var) || !__is_cond_ptr(_name); \
+	     ({ goto _label; }))                                \
+		if (0) {                                        \
+_label:                                                         \
+			break;                                  \
+		} else
 
 /*
  * DEFINE_GUARD(name, type, lock, unlock):
diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index 76e41805b92d..96e8a66da133 100644
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -43,7 +43,7 @@ extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
 extern int dump_align(struct coredump_params *cprm, int align);
 int dump_user_range(struct coredump_params *cprm, unsigned long start,
 		    unsigned long len);
-extern void do_coredump(const kernel_siginfo_t *siginfo);
+extern void vfs_coredump(const kernel_siginfo_t *siginfo);
 
 /*
  * Logging for the coredump code, ratelimited.
@@ -63,7 +63,7 @@ extern void do_coredump(const kernel_siginfo_t *siginfo);
 #define coredump_report_failure(fmt, ...) __COREDUMP_PRINTK(KERN_WARNING, fmt, ##__VA_ARGS__)
 
 #else
-static inline void do_coredump(const kernel_siginfo_t *siginfo) {}
+static inline void vfs_coredump(const kernel_siginfo_t *siginfo) {}
 
 #define coredump_report(...)
 #define coredump_report_failure(...)
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 5658a3bfe803..a102a10f833f 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -263,6 +263,8 @@ static inline void put_cred(const struct cred *cred)
 	put_cred_many(cred, 1);
 }
 
+DEFINE_FREE(put_cred, struct cred *, if (!IS_ERR_OR_NULL(_T)) put_cred(_T))
+
 /**
  * current_cred - Access the current task's subjective credentials
  *
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1b5212de5702..f0b18ca5f947 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3269,6 +3269,22 @@ static inline bool is_dot_dotdot(const char *name, size_t len)
 		(len == 1 || (len == 2 && name[1] == '.'));
 }
 
+/**
+ * name_contains_dotdot - check if a file name contains ".." path components
+ *
+ * Search for ".." surrounded by either '/' or start/end of string.
+ */
+static inline bool name_contains_dotdot(const char *name)
+{
+	size_t name_len;
+
+	name_len = strlen(name);
+	return strcmp(name, "..") == 0 ||
+	       strncmp(name, "../", 3) == 0 ||
+	       strstr(name, "/../") != NULL ||
+	       (name_len >= 3 && strcmp(name + name_len - 3, "/..") == 0);
+}
+
 #include <linux/err.h>
 
 /* needed for stackable file system support */
diff --git a/include/uapi/linux/coredump.h b/include/uapi/linux/coredump.h
new file mode 100644
index 000000000000..dc3789b78af0
--- /dev/null
+++ b/include/uapi/linux/coredump.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef _UAPI_LINUX_COREDUMP_H
+#define _UAPI_LINUX_COREDUMP_H
+
+#include <linux/types.h>
+
+/**
+ * coredump_{req,ack} flags
+ * @COREDUMP_KERNEL: kernel writes coredump
+ * @COREDUMP_USERSPACE: userspace writes coredump
+ * @COREDUMP_REJECT: don't generate coredump
+ * @COREDUMP_WAIT: wait for coredump server
+ */
+enum {
+	COREDUMP_KERNEL		= (1ULL << 0),
+	COREDUMP_USERSPACE	= (1ULL << 1),
+	COREDUMP_REJECT		= (1ULL << 2),
+	COREDUMP_WAIT		= (1ULL << 3),
+};
+
+/**
+ * struct coredump_req - message kernel sends to userspace
+ * @size: size of struct coredump_req
+ * @size_ack: known size of struct coredump_ack on this kernel
+ * @mask: supported features
+ *
+ * When a coredump happens the kernel will connect to the coredump
+ * socket and send a coredump request to the coredump server. The @size
+ * member is set to the size of struct coredump_req and provides a hint
+ * to userspace how much data can be read. Userspace may use MSG_PEEK to
+ * peek the size of struct coredump_req and then choose to consume it in
+ * one go. Userspace may also simply read a COREDUMP_ACK_SIZE_VER0
+ * request. If the size the kernel sends is larger userspace simply
+ * discards any remaining data.
+ *
+ * The coredump_req->mask member is set to the currently know features.
+ * Userspace may only set coredump_ack->mask to the bits raised by the
+ * kernel in coredump_req->mask.
+ *
+ * The coredump_req->size_ack member is set by the kernel to the size of
+ * struct coredump_ack the kernel knows. Userspace may only send up to
+ * coredump_req->size_ack bytes to the kernel and must set
+ * coredump_ack->size accordingly.
+ */
+struct coredump_req {
+	__u32 size;
+	__u32 size_ack;
+	__u64 mask;
+};
+
+enum {
+	COREDUMP_REQ_SIZE_VER0 = 16U, /* size of first published struct */
+};
+
+/**
+ * struct coredump_ack - message userspace sends to kernel
+ * @size: size of the struct
+ * @spare: unused
+ * @mask: features kernel is supposed to use
+ *
+ * The @size member must be set to the size of struct coredump_ack. It
+ * may never exceed what the kernel returned in coredump_req->size_ack
+ * but it may of course be smaller (>= COREDUMP_ACK_SIZE_VER0 and <=
+ * coredump_req->size_ack).
+ *
+ * The @mask member must be set to the features the coredump server
+ * wants the kernel to use. Only bits the kernel returned in
+ * coredump_req->mask may be set.
+ */
+struct coredump_ack {
+	__u32 size;
+	__u32 spare;
+	__u64 mask;
+};
+
+enum {
+	COREDUMP_ACK_SIZE_VER0 = 16U, /* size of first published struct */
+};
+
+/**
+ * enum coredump_mark - Markers for the coredump socket
+ *
+ * The kernel will place a single byte on the coredump socket. The
+ * markers notify userspace whether the coredump ack succeeded or
+ * failed.
+ *
+ * @COREDUMP_MARK_MINSIZE: the provided coredump_ack size was too small
+ * @COREDUMP_MARK_MAXSIZE: the provided coredump_ack size was too big
+ * @COREDUMP_MARK_UNSUPPORTED: the provided coredump_ack mask was invalid
+ * @COREDUMP_MARK_CONFLICTING: the provided coredump_ack mask has conflicting options
+ * @COREDUMP_MARK_REQACK: the coredump request and ack was successful
+ * @__COREDUMP_MARK_MAX: the maximum coredump mark value
+ */
+enum coredump_mark {
+	COREDUMP_MARK_REQACK		= 0U,
+	COREDUMP_MARK_MINSIZE		= 1U,
+	COREDUMP_MARK_MAXSIZE		= 2U,
+	COREDUMP_MARK_UNSUPPORTED	= 3U,
+	COREDUMP_MARK_CONFLICTING	= 4U,
+	__COREDUMP_MARK_MAX		= (1U << 31),
+};
+
+#endif /* _UAPI_LINUX_COREDUMP_H */