From 86c3afdf9759fce76ba228dddcd9ce185b0e429b Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Tue, 26 Oct 2021 17:20:15 -0400 Subject: [PATCH] binfmt_elf: Take the mmap lock when walking the VMA list I'm not sure if the VMA list can change under us, but dump_vma_snapshot() is very careful to take the mmap_lock in write mode. We only need to take it in read mode here as we do not care if the size of the stack VMA changes underneath us. If it can be changed underneath us, this is a potential use-after-free for a multithreaded process which is dumping core. Fixes: 2aa362c49c31 ("coredump: extend core dump note section to contain file names of mapped files") Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Liam R. Howlett --- fs/binfmt_elf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index d41cca755ff9f..5915518c8a1d9 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1652,6 +1652,7 @@ static int fill_files_note(struct memelfnote *note) name_base = name_curpos = ((char *)data) + names_ofs; remaining = size - names_ofs; count = 0; + mmap_read_lock(mm); for_each_vma(vmi, vma) { struct file *file; const char *filename; @@ -1662,6 +1663,7 @@ static int fill_files_note(struct memelfnote *note) filename = file_path(file, name_curpos, remaining); if (IS_ERR(filename)) { if (PTR_ERR(filename) == -ENAMETOOLONG) { + mmap_read_unlock(mm); kvfree(data); size = size * 5 / 4; goto alloc; @@ -1681,6 +1683,7 @@ static int fill_files_note(struct memelfnote *note) *start_end_ofs++ = vma->vm_pgoff; count++; } + mmap_read_unlock(mm); /* Now we know exact count of files, can store it */ data[0] = count; -- 2.50.1