[PATCH 6/7] binfmt_elf: remove the set_fs(KERNEL_DS) in elf_core_dump

Christoph Hellwig
2020-05-05T10:13:34Z

There is no logic in elf_core_dump itself or in the various arch helpers
called from it which use uaccess routines on kernel pointers except for
the file writes thate are nicely encapsulated by using __kernel_write in
dump_emit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/binfmt_elf.c | 16 +---------------
1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index a1f57e20c3cf2..ba6f87ba029a7 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1355,7 +1355,6 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
u32 __user *header = (u32 __user *) vma->vm_start;
u32 word;
- mm_segment_t fs = get_fs();
/*
* Doing it this way gets the constant folded by GCC.
*/
@@ -1368,14 +1367,8 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
magic.elfmag[EI_MAG1] = ELFMAG1;
magic.elfmag[EI_MAG2] = ELFMAG2;
magic.elfmag[EI_MAG3] = ELFMAG3;
- /*
- * Switch to the user "segment" for get_user(),
- * then put back what elf_core_dump() had in place.
- */
- set_fs(USER_DS);
if (unlikely(get_user(word, header)))
word = 0;
- set_fs(fs);
if (word == magic.cmp)
return PAGE_SIZE;
}
@@ -2183,7 +2176,6 @@ static void fill_extnum_info(struct elfhdr *elf, struct elf_shdr *shdr4extnum,
static int elf_core_dump(struct coredump_params *cprm)
{
int has_dumped = 0;
- mm_segment_t fs;
int segs, i;
size_t vma_data_size = 0;
struct vm_area_struct *vma, *gate_vma;
@@ -2232,13 +2224,10 @@ static int elf_core_dump(struct coredump_params *cprm)
* notes. This also sets up the file header.
*/
if (!fill_note_info(&elf, e_phnum, &info, cprm->siginfo, cprm->regs))
- goto cleanup;
+ goto end_coredump;

has_dumped = 1;

- fs = get_fs();
- set_fs(KERNEL_DS);
-
offset += sizeof(elf); /* Elf header */
offset += segs * sizeof(struct elf_phdr); /* Program headers */

@@ -2366,9 +2355,6 @@ static int elf_core_dump(struct coredump_params *cprm)
}

end_coredump:
- set_fs(fs);
-
-cleanup:
free_note_info(&info);
kfree(shdr4extnum);
kvfree(vma_filesz);
--
2.26.2