git: 5be8c23a343f - stable/13 - elfdump: handle small files more gracefully

The branch stable/13 has been updated by vangyzen:

URL: https://cgit.FreeBSD.org/src/commit/?id=5be8c23a343f1c4dc60a4b48e3e3832e146aaacb

commit 5be8c23a343f1c4dc60a4b48e3e3832e146aaacb
Author:     Eric van Gyzen <vangyzen@FreeBSD.org>
AuthorDate: 2022-02-17 15:53:48 +0000
Commit:     Eric van Gyzen <vangyzen@FreeBSD.org>
CommitDate: 2022-03-02 21:56:31 +0000

    elfdump: handle small files more gracefully
    
    elfdump -E on an empty file would complain "Invalid argument" because
    it tried to mmap zero bytes.  With the -E flag, elfdump should
    simply exit non-zero.  For tiny files, the code would reference off
    the end of the mapped region.
    
    Ensure the file is large enough to contain an ELF header before mapping it.
    
    MFC after:      1 week
    Sponsored by:   Dell EMC Isilon
    
    (cherry picked from commit 86e5e10daf54da7df358a06033f3a3bd8c852a08)
---
 usr.bin/elfdump/elfdump.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/usr.bin/elfdump/elfdump.c b/usr.bin/elfdump/elfdump.c
index 2bdf98830088..28b42a55a508 100644
--- a/usr.bin/elfdump/elfdump.c
+++ b/usr.bin/elfdump/elfdump.c
@@ -585,6 +585,11 @@ main(int ac, char **av)
 	if ((fd = open(*av, O_RDONLY)) < 0 ||
 	    fstat(fd, &sb) < 0)
 		err(1, "%s", *av);
+	if ((size_t)sb.st_size < sizeof(Elf32_Ehdr)) {
+		if (flags & ED_IS_ELF)
+			exit(1);
+		errx(1, "not an elf file");
+	}
 	cap_rights_init(&rights, CAP_MMAP_R);
 	if (caph_rights_limit(fd, &rights) < 0)
 		err(1, "unable to limit rights for %s", *av);
@@ -598,7 +603,7 @@ main(int ac, char **av)
 	e = mmap(NULL, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
 	if (e == MAP_FAILED)
 		err(1, NULL);
-	if (!IS_ELF(*(Elf32_Ehdr *)e)) {
+	if (!IS_ELF(*e)) {
 		if (flags & ED_IS_ELF)
 			exit(1);
 		errx(1, "not an elf file");