MIPS: Module: Deal with malformed HI16/LO16 relocation sequences.

In case a series of R_MIPS_HI16 relocations was not followed by an
R_MIPS_LO16 relocation we were leaking the hi16 relocation chain.
Handle that error and return an error.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 28 insertions, 7 deletions

diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index 8e1fb802c3e..4f8c3cba8c0 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -140,19 +140,30 @@ static int apply_r_mips_hi16_rela(struct module *me, u32 *location, Elf_Addr v)
         return 0;
 }
 
+static void free_relocation_chain(struct mips_hi16 *l)
+{
+        struct mips_hi16 *next;
+
+        while (l) {
+                next = l->next;
+                kfree(l);
+                l = next;
+        }
+}
+
 static int apply_r_mips_lo16_rel(struct module *me, u32 *location, Elf_Addr v)
 {
         unsigned long insnlo = *location;
+        struct mips_hi16 *l;
         Elf_Addr val, vallo;
-        struct mips_hi16 *l, *next;
 
         /* Sign extend the addend we extract from the lo insn.  */
         vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
 
         if (me->arch.r_mips_hi16_list != NULL) {
-
                 l = me->arch.r_mips_hi16_list;
                 while (l != NULL) {
+                        struct mips_hi16 *next;
                         unsigned long insn;
 
                         /*
@@ -198,11 +209,8 @@ static int apply_r_mips_lo16_rel(struct module *me, u32 *location, Elf_Addr v)
         return 0;
 
 out_danger:
-        while (l) {
-                next = l->next;
-                kfree(l);
-                l = next;
-        }
+        free_relocation_chain(l);
+        me->arch.r_mips_hi16_list = NULL;
 
         pr_err("module %s: dangerous R_MIPS_LO16 REL relocation\n", me->name);
 
@@ -300,6 +308,19 @@ int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
                         return res;
         }
 
+        /*
+         * Normally the hi16 list should be deallocated at this point.  A
+         * malformed binary however could contain a series of R_MIPS_HI16
+         * relocations not followed by a R_MIPS_LO16 relocation.  In that
+         * case, free up the list and return an error.
+         */
+        if (me->arch.r_mips_hi16_list) {
+                free_relocation_chain(me->arch.r_mips_hi16_list);
+                me->arch.r_mips_hi16_list = NULL;
+
+                return -ENOEXEC;
+        }
+
         return 0;
 }