[PATCH] binfmt_elf: use check_mul_overflow() for size calc

[Pranav Tyagi <pranav.tyagi03@gmail.com>]

Use check_mul_overflow() to safely compute the total size of ELF program
headers instead of relying on direct multiplication.

Directly multiplying sizeof(struct elf_phdr) with e_phnum risks integer
overflow, especially on 32-bit systems or with malformed ELF binaries
crafted to trigger wrap-around. If an overflow occurs, kmalloc() could
allocate insufficient memory, potentially leading to out-of-bound
accesses, memory corruption or security vulnerabilities.

Using check_mul_overflow() ensures the multiplication is performed
safely and detects overflows before memory allocation. This change makes
the function more robust when handling untrusted or corrupted binaries.

Signed-off-by: Pranav Tyagi <pranav.tyagi03@gmail.com>
Link: https://github.com/KSPP/linux/issues/92
---
 fs/binfmt_elf.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index a43363d593e5..774e705798b8 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -518,7 +518,10 @@ static struct elf_phdr *load_elf_phdrs(const struct elfhdr *elf_ex,
 
 	/* Sanity check the number of program headers... */
 	/* ...and their total size. */
-	size = sizeof(struct elf_phdr) * elf_ex->e_phnum;
+	
+	if (check_mul_overflow(sizeof(struct elf_phdr), elf_ex->e_phnum, &size))
+		goto out;
+
 	if (size == 0 || size > 65536 || size > ELF_MIN_ALIGN)
 		goto out;
 
-- 
2.49.0