Messages in this thread | | | Subject | Re: [merged] exec-open-code-copy_string_kernel.patch removed from -mm tree | From | Vegard Nossum <> | Date | Tue, 16 Jun 2020 15:14:44 +0200 |
| |
On 2020-06-05 22:19, akpm@linux-foundation.org wrote: > The patch titled > Subject: exec: open code copy_string_kernel > has been removed from the -mm tree. Its filename was > exec-open-code-copy_string_kernel.patch > > This patch was dropped because it was merged into mainline or a subsystem tree > > ------------------------------------------------------ > From: Christoph Hellwig <hch@lst.de> > Subject: exec: open code copy_string_kernel > > Currently copy_string_kernel is just a wrapper around copy_strings that > simplifies the calling conventions and uses set_fs to allow passing a > kernel pointer. But due to the fact the we only need to handle a single > kernel argument pointer, the logic can be sigificantly simplified while > getting rid of the set_fs. > > Link: http://lkml.kernel.org/r/20200501104105.2621149-3-hch@lst.de > Signed-off-by: Christoph Hellwig <hch@lst.de> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > fs/exec.c | 45 +++++++++++++++++++++++++++++++++++---------- > 1 file changed, 35 insertions(+), 10 deletions(-) > > --- a/fs/exec.c~exec-open-code-copy_string_kernel > +++ a/fs/exec.c > @@ -592,17 +592,42 @@ out: > */ > int copy_string_kernel(const char *arg, struct linux_binprm *bprm) > { > - int r; > - mm_segment_t oldfs = get_fs(); > - struct user_arg_ptr argv = { > - .ptr.native = (const char __user *const __user *)&arg, > - }; > - > - set_fs(KERNEL_DS); > - r = copy_strings(1, argv, bprm); > - set_fs(oldfs); > + int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */; > + unsigned long pos = bprm->p; > > - return r; > + if (len == 0) > + return -EFAULT;
Just a quick question, how can len ever be 0 here when len was set to strnlen() + 1? Should the test be different?
The old version (i.e. copy_strings()) seems to return -EFAULT when strnlen() returns 0.
Vegard
> + if (!valid_arg_len(bprm, len)) > + return -E2BIG; > + > + /* We're going to work our way backwards. */ > + arg += len; > + bprm->p -= len; > + if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin) > + return -E2BIG; > + > + while (len > 0) { > + unsigned int bytes_to_copy = min_t(unsigned int, len, > + min_not_zero(offset_in_page(pos), PAGE_SIZE)); > + struct page *page; > + char *kaddr; > + > + pos -= bytes_to_copy; > + arg -= bytes_to_copy; > + len -= bytes_to_copy; > + > + page = get_arg_page(bprm, pos, 1); > + if (!page) > + return -E2BIG; > + kaddr = kmap_atomic(page); > + flush_arg_page(bprm, pos & PAGE_MASK, page); > + memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy); > + flush_kernel_dcache_page(page); > + kunmap_atomic(kaddr); > + put_arg_page(page); > + } > + > + return 0; > } > EXPORT_SYMBOL(copy_string_kernel); >
| |