[patch 50/86] fs/binfmt_elf.c: extract elf_read() function

Andrew Morton
2019-12-05T00:52:27Z

From: Alexey Dobriyan <adobriyan@gmail.com>
Subject: fs/binfmt_elf.c: extract elf_read() function

ELF reads done by the kernel have very complicated error detection code
which better live in one place.

Link: http://lkml.kernel.org/r/20191005165215.GB26927@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

fs/binfmt_elf.c | 49 ++++++++++++++++++++++------------------------
1 file changed, 24 insertions(+), 25 deletions(-)

--- a/fs/binfmt_elf.c~elf-extract-elf_read-function
+++ a/fs/binfmt_elf.c
@@ -404,6 +404,17 @@ static unsigned long total_mapping_size(
ELF_PAGESTART(cmds[first_idx].p_vaddr);
}

+static int elf_read(struct file *file, void *buf, size_t len, loff_t pos)
+{
+ ssize_t rv;
+
+ rv = kernel_read(file, buf, len, &pos);
+ if (unlikely(rv != len)) {
+ return (rv < 0) ? rv : -EIO;
+ }
+ return 0;
+}
+
/**
* load_elf_phdrs() - load ELF program headers
* @elf_ex: ELF header of the binary whose program headers should be loaded
@@ -418,7 +429,6 @@ static struct elf_phdr *load_elf_phdrs(c
{
struct elf_phdr *elf_phdata = NULL;
int retval, err = -1;
- loff_t pos = elf_ex->e_phoff;
unsigned int size;

/*
@@ -439,9 +449,9 @@ static struct elf_phdr *load_elf_phdrs(c
goto out;

/* Read in the program headers */
- retval = kernel_read(elf_file, elf_phdata, size, &pos);
- if (retval != size) {
- err = (retval < 0) ? retval : -EIO;
+ retval = elf_read(elf_file, elf_phdata, size, elf_ex->e_phoff);
+ if (retval < 0) {
+ err = retval;
goto out;
}

@@ -720,7 +730,6 @@ static int load_elf_binary(struct linux_
elf_ppnt = elf_phdata;
for (i = 0; i < loc->elf_ex.e_phnum; i++, elf_ppnt++) {
char *elf_interpreter;
- loff_t pos;

if (elf_ppnt->p_type != PT_INTERP)
continue;
@@ -738,14 +747,10 @@ static int load_elf_binary(struct linux_
if (!elf_interpreter)
goto out_free_ph;

- pos = elf_ppnt->p_offset;
- retval = kernel_read(bprm->file, elf_interpreter,
- elf_ppnt->p_filesz, &pos);
- if (retval != elf_ppnt->p_filesz) {
- if (retval >= 0)
- retval = -EIO;
+ retval = elf_read(bprm->file, elf_interpreter, elf_ppnt->p_filesz,
+ elf_ppnt->p_offset);
+ if (retval < 0)
goto out_free_interp;
- }
/* make sure path is NULL terminated */
retval = -ENOEXEC;
if (elf_interpreter[elf_ppnt->p_filesz - 1] != '\0')
@@ -764,14 +769,10 @@ static int load_elf_binary(struct linux_
would_dump(bprm, interpreter);

/* Get the exec headers */
- pos = 0;
- retval = kernel_read(interpreter, &loc->interp_elf_ex,
- sizeof(loc->interp_elf_ex), &pos);
- if (retval != sizeof(loc->interp_elf_ex)) {
- if (retval >= 0)
- retval = -EIO;
+ retval = elf_read(interpreter, &loc->interp_elf_ex,
+ sizeof(loc->interp_elf_ex), 0);
+ if (retval < 0)
goto out_free_dentry;
- }

break;

@@ -1174,11 +1175,10 @@ static int load_elf_library(struct file
unsigned long elf_bss, bss, len;
int retval, error, i, j;
struct elfhdr elf_ex;
- loff_t pos = 0;

error = -ENOEXEC;
- retval = kernel_read(file, &elf_ex, sizeof(elf_ex), &pos);
- if (retval != sizeof(elf_ex))
+ retval = elf_read(file, &elf_ex, sizeof(elf_ex), 0);
+ if (retval < 0)
goto out;

if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
@@ -1203,9 +1203,8 @@ static int load_elf_library(struct file

eppnt = elf_phdata;
error = -ENOEXEC;
- pos = elf_ex.e_phoff;
- retval = kernel_read(file, eppnt, j, &pos);
- if (retval != j)
+ retval = elf_read(file, eppnt, j, elf_ex.e_phoff);
+ if (retval < 0)
goto out_free_ph;

for (j = 0, i = 0; i<elf_ex.e_phnum; i++)
_