thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 198 insertions, 0 deletions

diff --git a/scripts/elf-parse.c b/scripts/elf-parse.c
new file mode 100644
index 000000000..99869ff91
--- /dev/null
+++ b/scripts/elf-parse.c
@@ -0,0 +1,198 @@
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "elf-parse.h"
+
+struct elf_funcs elf_parser;
+
+/*
+ * Get the whole file as a programming convenience in order to avoid
+ * malloc+lseek+read+free of many pieces.  If successful, then mmap
+ * avoids copying unused pieces; else just read the whole file.
+ * Open for both read and write.
+ */
+static void *map_file(char const *fname, size_t *size)
+{
+	int fd;
+	struct stat sb;
+	void *addr = NULL;
+
+	fd = open(fname, O_RDWR);
+	if (fd < 0) {
+		perror(fname);
+		return NULL;
+	}
+	if (fstat(fd, &sb) < 0) {
+		perror(fname);
+		goto out;
+	}
+	if (!S_ISREG(sb.st_mode)) {
+		fprintf(stderr, "not a regular file: %s\n", fname);
+		goto out;
+	}
+
+	addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+	if (addr == MAP_FAILED) {
+		fprintf(stderr, "Could not mmap file: %s\n", fname);
+		goto out;
+	}
+
+	*size = sb.st_size;
+
+out:
+	close(fd);
+	return addr;
+}
+
+static int elf_parse(const char *fname, void *addr, uint32_t types)
+{
+	Elf_Ehdr *ehdr = addr;
+	uint16_t type;
+
+	switch (ehdr->e32.e_ident[EI_DATA]) {
+	case ELFDATA2LSB:
+		elf_parser.r	= rle;
+		elf_parser.r2	= r2le;
+		elf_parser.r8	= r8le;
+		elf_parser.w	= wle;
+		elf_parser.w8	= w8le;
+		break;
+	case ELFDATA2MSB:
+		elf_parser.r	= rbe;
+		elf_parser.r2	= r2be;
+		elf_parser.r8	= r8be;
+		elf_parser.w	= wbe;
+		elf_parser.w8	= w8be;
+		break;
+	default:
+		fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
+			ehdr->e32.e_ident[EI_DATA], fname);
+		return -1;
+	}
+
+	if (memcmp(ELFMAG, ehdr->e32.e_ident, SELFMAG) != 0 ||
+	    ehdr->e32.e_ident[EI_VERSION] != EV_CURRENT) {
+		fprintf(stderr, "unrecognized ELF file %s\n", fname);
+		return -1;
+	}
+
+	type = elf_parser.r2(&ehdr->e32.e_type);
+	if (!((1 << type) & types)) {
+		fprintf(stderr, "Invalid ELF type file %s\n", fname);
+		return -1;
+	}
+
+	switch (ehdr->e32.e_ident[EI_CLASS]) {
+	case ELFCLASS32: {
+		elf_parser.ehdr_shoff		= ehdr32_shoff;
+		elf_parser.ehdr_shentsize	= ehdr32_shentsize;
+		elf_parser.ehdr_shstrndx	= ehdr32_shstrndx;
+		elf_parser.ehdr_shnum		= ehdr32_shnum;
+		elf_parser.shdr_addr		= shdr32_addr;
+		elf_parser.shdr_offset		= shdr32_offset;
+		elf_parser.shdr_link		= shdr32_link;
+		elf_parser.shdr_size		= shdr32_size;
+		elf_parser.shdr_name		= shdr32_name;
+		elf_parser.shdr_type		= shdr32_type;
+		elf_parser.shdr_entsize		= shdr32_entsize;
+		elf_parser.sym_type		= sym32_type;
+		elf_parser.sym_name		= sym32_name;
+		elf_parser.sym_value		= sym32_value;
+		elf_parser.sym_shndx		= sym32_shndx;
+		elf_parser.rela_offset		= rela32_offset;
+		elf_parser.rela_info		= rela32_info;
+		elf_parser.rela_addend		= rela32_addend;
+		elf_parser.rela_write_addend	= rela32_write_addend;
+
+		if (elf_parser.r2(&ehdr->e32.e_ehsize) != sizeof(Elf32_Ehdr) ||
+		    elf_parser.r2(&ehdr->e32.e_shentsize) != sizeof(Elf32_Shdr)) {
+			fprintf(stderr,
+				"unrecognized ET_EXEC/ET_DYN file: %s\n", fname);
+			return -1;
+		}
+
+		}
+		break;
+	case ELFCLASS64: {
+		elf_parser.ehdr_shoff		= ehdr64_shoff;
+		elf_parser.ehdr_shentsize		= ehdr64_shentsize;
+		elf_parser.ehdr_shstrndx		= ehdr64_shstrndx;
+		elf_parser.ehdr_shnum		= ehdr64_shnum;
+		elf_parser.shdr_addr		= shdr64_addr;
+		elf_parser.shdr_offset		= shdr64_offset;
+		elf_parser.shdr_link		= shdr64_link;
+		elf_parser.shdr_size		= shdr64_size;
+		elf_parser.shdr_name		= shdr64_name;
+		elf_parser.shdr_type		= shdr64_type;
+		elf_parser.shdr_entsize		= shdr64_entsize;
+		elf_parser.sym_type		= sym64_type;
+		elf_parser.sym_name		= sym64_name;
+		elf_parser.sym_value		= sym64_value;
+		elf_parser.sym_shndx		= sym64_shndx;
+		elf_parser.rela_offset		= rela64_offset;
+		elf_parser.rela_info		= rela64_info;
+		elf_parser.rela_addend		= rela64_addend;
+		elf_parser.rela_write_addend	= rela64_write_addend;
+
+		if (elf_parser.r2(&ehdr->e64.e_ehsize) != sizeof(Elf64_Ehdr) ||
+		    elf_parser.r2(&ehdr->e64.e_shentsize) != sizeof(Elf64_Shdr)) {
+			fprintf(stderr,
+				"unrecognized ET_EXEC/ET_DYN file: %s\n",
+				fname);
+			return -1;
+		}
+
+		}
+		break;
+	default:
+		fprintf(stderr, "unrecognized ELF class %d %s\n",
+			ehdr->e32.e_ident[EI_CLASS], fname);
+		return -1;
+	}
+	return 0;
+}
+
+int elf_map_machine(void *addr)
+{
+	Elf_Ehdr *ehdr = addr;
+
+	return elf_parser.r2(&ehdr->e32.e_machine);
+}
+
+int elf_map_long_size(void *addr)
+{
+	Elf_Ehdr *ehdr = addr;
+
+	return ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
+}
+
+void *elf_map(char const *fname, size_t *size, uint32_t types)
+{
+	void *addr;
+	int ret;
+
+	addr = map_file(fname, size);
+	if (!addr)
+		return NULL;
+
+	ret = elf_parse(fname, addr, types);
+	if (ret < 0) {
+		elf_unmap(addr, *size);
+		return NULL;
+	}
+
+	return addr;
+}
+
+void elf_unmap(void *addr, size_t size)
+{
+	munmap(addr, size);
+}