Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jann Horn <jannh@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Oleg Nesterov <oleg@redhat.com>
Subject: [PATCH v4 3/5] coredump: Refactor page range dumping into common helper
Date: Wed, 26 Aug 2020 17:14:46 +0200	[thread overview]
Message-ID: <20200826151448.3404695-4-jannh@google.com> (raw)
In-Reply-To: <20200826151448.3404695-1-jannh@google.com>

Both fs/binfmt_elf.c and fs/binfmt_elf_fdpic.c need to dump ranges of pages
into the coredump file. Extract that logic into a common helper.

Signed-off-by: Jann Horn <jannh@google.com>
---
 fs/binfmt_elf.c          | 22 ++--------------------
 fs/binfmt_elf_fdpic.c    | 18 +++---------------
 fs/coredump.c            | 34 ++++++++++++++++++++++++++++++++++
 include/linux/coredump.h |  2 ++
 4 files changed, 41 insertions(+), 35 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 13d053982dd7..5fd11a25d320 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2419,26 +2419,8 @@ static int elf_core_dump(struct coredump_params *cprm)
 
 	for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
 			vma = next_vma(vma, gate_vma)) {
-		unsigned long addr;
-		unsigned long end;
-
-		end = vma->vm_start + vma_filesz[i++];
-
-		for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) {
-			struct page *page;
-			int stop;
-
-			page = get_dump_page(addr);
-			if (page) {
-				void *kaddr = kmap(page);
-				stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
-				kunmap(page);
-				put_page(page);
-			} else
-				stop = !dump_skip(cprm, PAGE_SIZE);
-			if (stop)
-				goto end_coredump;
-		}
+		if (!dump_user_range(cprm, vma->vm_start, vma_filesz[i++]))
+			goto end_coredump;
 	}
 	dump_truncate(cprm);
 
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index a53f83830986..76e8c0defdc8 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1534,21 +1534,9 @@ static bool elf_fdpic_dump_segments(struct coredump_params *cprm)
 		if (!maydump(vma, cprm->mm_flags))
 			continue;
 
-		for (addr = vma->vm_start; addr < vma->vm_end;
-							addr += PAGE_SIZE) {
-			bool res;
-			struct page *page = get_dump_page(addr);
-			if (page) {
-				void *kaddr = kmap(page);
-				res = dump_emit(cprm, kaddr, PAGE_SIZE);
-				kunmap(page);
-				put_page(page);
-			} else {
-				res = dump_skip(cprm, PAGE_SIZE);
-			}
-			if (!res)
-				return false;
-		}
+		if (!dump_user_range(cprm, vma->vm_start,
+				     vma->vma_end - vma->vm_start))
+			return false;
 	}
 	return true;
 }
diff --git a/fs/coredump.c b/fs/coredump.c
index 5e24c06092c9..6042d15acd51 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -876,6 +876,40 @@ int dump_skip(struct coredump_params *cprm, size_t nr)
 }
 EXPORT_SYMBOL(dump_skip);
 
+#ifdef CONFIG_ELF_CORE
+int dump_user_range(struct coredump_params *cprm, unsigned long start,
+		    unsigned long len)
+{
+	unsigned long addr;
+
+	for (addr = start; addr < start + len; addr += PAGE_SIZE) {
+		struct page *page;
+		int stop;
+
+		/*
+		 * To avoid having to allocate page tables for virtual address
+		 * ranges that have never been used yet, and also to make it
+		 * easy to generate sparse core files, use a helper that returns
+		 * NULL when encountering an empty page table entry that would
+		 * otherwise have been filled with the zero page.
+		 */
+		page = get_dump_page(addr);
+		if (page) {
+			void *kaddr = kmap(page);
+
+			stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
+			kunmap(page);
+			put_page(page);
+		} else {
+			stop = !dump_skip(cprm, PAGE_SIZE);
+		}
+		if (stop)
+			return 0;
+	}
+	return 1;
+}
+#endif
+
 int dump_align(struct coredump_params *cprm, int align)
 {
 	unsigned mod = cprm->pos & (align - 1);
diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index 7a899e83835d..f0b71a74d0bc 100644
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -16,6 +16,8 @@ extern int dump_skip(struct coredump_params *cprm, size_t nr);
 extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
 extern int dump_align(struct coredump_params *cprm, int align);
 extern void dump_truncate(struct coredump_params *cprm);
+int dump_user_range(struct coredump_params *cprm, unsigned long start,
+		    unsigned long len);
 #ifdef CONFIG_COREDUMP
 extern void do_coredump(const kernel_siginfo_t *siginfo);
 #else
-- 
2.28.0.297.g1956fa8f8d-goog


  parent reply	other threads:[~2020-08-26 15:16 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-26 15:14 [PATCH v4 0/5] Fix ELF / FDPIC ELF core dumping, and use mmap_lock properly in there Jann Horn
2020-08-26 15:14 ` [PATCH v4 1/5] binfmt_elf_fdpic: Stop using dump_emit() on user pointers on !MMU Jann Horn
2020-08-26 15:14 ` [PATCH v4 2/5] coredump: Let dump_emit() bail out on short writes Jann Horn
2020-08-26 15:14 ` Jann Horn [this message]
2020-08-26 15:14 ` [PATCH v4 4/5] binfmt_elf, binfmt_elf_fdpic: Use a VMA list snapshot Jann Horn
2020-08-26 17:14   ` Linus Torvalds
2020-08-26 15:14 ` [PATCH v4 5/5] mm/gup: Take mmap_lock in get_dump_page() Jann Horn
2020-08-26 17:15 ` [PATCH v4 0/5] Fix ELF / FDPIC ELF core dumping, and use mmap_lock properly in there Linus Torvalds

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200826151448.3404695-4-jannh@google.com \
    --to=jannh@google.com \
    --cc=akpm@linux-foundation.org \
    --cc=ebiederm@xmission.com \
    --cc=hch@lst.de \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=oleg@redhat.com \
    --cc=torvalds@linux-foundation.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [PATCH v4 3/5] coredump: Refactor page range dumping into common helper' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).