fdpic: check that the size returned by kernel_read() is what we asked for

Check that the size of the read returned by kernel_read() is what we asked
for.  If it isn't, then reject the binary as being a badly formatted.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 32649f2a1654..ddd35d873391 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -136,8 +136,8 @@ static int elf_fdpic_fetch_phdrs(struct elf_fdpic_params *params,
 
         retval = kernel_read(file, params->hdr.e_phoff,
                              (char *) params->phdrs, size);
-        if (retval < 0)
-                return retval;
+        if (unlikely(retval != size))
+                return retval < 0 ? retval : -ENOEXEC;
 
         /* determine stack size for this binary */
         phdr = params->phdrs;
@@ -218,8 +218,11 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm,
                                              phdr->p_offset,
                                              interpreter_name,
                                              phdr->p_filesz);
-                        if (retval < 0)
+                        if (unlikely(retval != phdr->p_filesz)) {
+                                if (retval >= 0)
+                                        retval = -ENOEXEC;
                                 goto error;
+                        }
 
                         retval = -ENOENT;
                         if (interpreter_name[phdr->p_filesz - 1] != '\0')
@@ -245,8 +248,11 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm,
 
                         retval = kernel_read(interpreter, 0, bprm->buf,
                                              BINPRM_BUF_SIZE);
-                        if (retval < 0)
+                        if (unlikely(retval != BINPRM_BUF_SIZE)) {
+                                if (retval >= 0)
+                                        retval = -ENOEXEC;
                                 goto error;
+                        }
 
                         interp_params.hdr = *((struct elfhdr *) bprm->buf);
                         break;