+ elf-fix-overflow-in-total-mapping-size-calculation.patch added to -mm tree

+ elf-fix-overflow-in-total-mapping-size-calculation.patch added to -mm tree

[akpm]

The patch titled
     Subject: ELF: fix overflow in total mapping size calculation
has been added to the -mm tree.  Its filename is
     elf-fix-overflow-in-total-mapping-size-calculation.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/elf-fix-overflow-in-total-mapping-size-calculation.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/elf-fix-overflow-in-total-mapping-size-calculation.patch

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------------------------------------------------------
From: Alexey Dobriyan <adobriyan@gmail.com>
Subject: ELF: fix overflow in total mapping size calculation

Kernel assumes that ELF program headers are ordered by mapping address,
but doesn't enforce it.  It is possible to make mapping size extremely
huge by simply shuffling first and last PT_LOAD segments.

As long as PT_LOAD segments do not overlap, it is silly to require sorting
by v_addr anyway because mmap() doesn't care.

Don't assume PT_LOAD segments are sorted and calculate min and max
addresses correctly.

Link: https://lkml.kernel.org/r/YVmd7D0M6G/DcP4O@localhost.localdomain
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/binfmt_elf.c |   23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

--- a/fs/binfmt_elf.c~elf-fix-overflow-in-total-mapping-size-calculation
+++ a/fs/binfmt_elf.c
@@ -93,7 +93,7 @@ static int elf_core_dump(struct coredump
 #define ELF_CORE_EFLAGS	0
 #endif
 
-#define ELF_PAGESTART(_v) ((_v) & ~(unsigned long)(ELF_MIN_ALIGN-1))
+#define ELF_PAGESTART(_v) ((_v) & ~(int)(ELF_MIN_ALIGN-1))
 #define ELF_PAGEOFFSET(_v) ((_v) & (ELF_MIN_ALIGN-1))
 #define ELF_PAGEALIGN(_v) (((_v) + ELF_MIN_ALIGN - 1) & ~(ELF_MIN_ALIGN - 1))
 
@@ -399,22 +399,21 @@ static unsigned long elf_map(struct file
 	return(map_addr);
 }
 
-static unsigned long total_mapping_size(const struct elf_phdr *cmds, int nr)
+static unsigned long total_mapping_size(const struct elf_phdr *phdr, int nr)
 {
-	int i, first_idx = -1, last_idx = -1;
+	elf_addr_t min_addr = -1;
+	elf_addr_t max_addr = 0;
+	bool pt_load = false;
+	int i;
 
 	for (i = 0; i < nr; i++) {
-		if (cmds[i].p_type == PT_LOAD) {
-			last_idx = i;
-			if (first_idx == -1)
-				first_idx = i;
+		if (phdr[i].p_type == PT_LOAD) {
+			min_addr = min(min_addr, ELF_PAGESTART(phdr[i].p_vaddr));
+			max_addr = max(max_addr, phdr[i].p_vaddr + phdr[i].p_memsz);
+			pt_load = true;
 		}
 	}
-	if (first_idx == -1)
-		return 0;
-
-	return cmds[last_idx].p_vaddr + cmds[last_idx].p_memsz -
-				ELF_PAGESTART(cmds[first_idx].p_vaddr);
+	return pt_load ? (max_addr - min_addr) : 0;
 }
 
 static int elf_read(struct file *file, void *buf, size_t len, loff_t pos)
_

Patches currently in -mm which might be from adobriyan@gmail.com are

lib-uninline-simple_strntoull-as-well.patch
elf-fix-overflow-in-total-mapping-size-calculation.patch