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binfmt_elf: remove the set_fs(KERNEL_DS) in elf_core_dump 

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>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2020-05-05 12:12:55 +02:00 committed by Al Viro
parent fa4751f454
commit d2530b436f
1 changed files with 1 additions and 15 deletions
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16
fs/binfmt_elf.c
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@ -1355,7 +1355,6 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) { vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
u32 __user *header = (u32 __user *) vma->vm_start; u32 __user *header = (u32 __user *) vma->vm_start;
u32 word; u32 word;
mm_segment_t fs = get_fs();
/* /*
* Doing it this way gets the constant folded by GCC. * 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_MAG1] = ELFMAG1;
magic.elfmag[EI_MAG2] = ELFMAG2; magic.elfmag[EI_MAG2] = ELFMAG2;
magic.elfmag[EI_MAG3] = ELFMAG3; 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))) if (unlikely(get_user(word, header)))
word = 0; word = 0;
set_fs(fs);
if (word == magic.cmp) if (word == magic.cmp)
return PAGE_SIZE; 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) static int elf_core_dump(struct coredump_params *cprm)
{ {
int has_dumped = 0; int has_dumped = 0;
mm_segment_t fs;
int segs, i; int segs, i;
size_t vma_data_size = 0; size_t vma_data_size = 0;
struct vm_area_struct *vma, *gate_vma; 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. * notes. This also sets up the file header.
*/ */
if (!fill_note_info(&elf, e_phnum, &info, cprm->siginfo, cprm->regs)) if (!fill_note_info(&elf, e_phnum, &info, cprm->siginfo, cprm->regs))
goto cleanup; goto end_coredump;
has_dumped = 1; has_dumped = 1;
fs = get_fs();
set_fs(KERNEL_DS);
offset += sizeof(elf); /* Elf header */ offset += sizeof(elf); /* Elf header */
offset += segs * sizeof(struct elf_phdr); /* Program headers */ offset += segs * sizeof(struct elf_phdr); /* Program headers */
@ -2366,9 +2355,6 @@ static int elf_core_dump(struct coredump_params *cprm)
} }
end_coredump: end_coredump:
set_fs(fs);
cleanup:
free_note_info(&info); free_note_info(&info);
kfree(shdr4extnum); kfree(shdr4extnum);
kvfree(vma_filesz); kvfree(vma_filesz);