[PATCH] fs/binfmt_elf: disallow e_phnum that equals zero

[Itay Ie <ieitayie@gmail.com>]

The elf_ex.e_phnum field can be set to zero.

If elf_ex.e_phnum is set to zero, then a redundant kmalloc with the size
zero is called and a following kfree. Check if elf_ex.e_phnum equals zero,
and prevent the redundant kmalloc and kfree.

Signed-off-by: Itay Ie <ieitayie@gmail.com>
---
 fs/binfmt_elf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 187b3f2b9202..f25e8f241ae9 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1348,7 +1348,8 @@ static int load_elf_library(struct file *file)

 	/* First of all, some simple consistency checks */
 	if (elf_ex.e_type != ET_EXEC || elf_ex.e_phnum > 2 ||
-	    !elf_check_arch(&elf_ex) || !file->f_op->mmap)
+	    elf_ex.e_phnum == 0 || !elf_check_arch(&elf_ex) ||
+	    !file->f_op->mmap)
 		goto out;
 	if (elf_check_fdpic(&elf_ex))
 		goto out;
@@ -1356,7 +1357,7 @@ static int load_elf_library(struct file *file)
 	/* Now read in all of the header information */

 	j = sizeof(struct elf_phdr) * elf_ex.e_phnum;
-	/* j < ELF_MIN_ALIGN because elf_ex.e_phnum <= 2 */
+	/* j < ELF_MIN_ALIGN because elf_ex.e_phnum is 1 or 2 */

 	error = -ENOMEM;
 	elf_phdata = kmalloc(j, GFP_KERNEL);
--
2.32.0