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authorOleg Nesterov <oleg@redhat.com>2017-10-03 16:15:55 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-10-03 17:54:25 -0700
commit43a4f2619038002f48c78698c42c05692d4b4eb2 (patch)
treeca46e0bb1cbd6a522131f473ce7d7a4d9fe64a43
parenteb23aa0317eb1f08e8d9d36b8753d42f03b32764 (diff)
downloadlinux-43a4f2619038002f48c78698c42c05692d4b4eb2.tar.bz2
exec: binfmt_misc: fix race between load_misc_binary() and kill_node()
load_misc_binary() makes a local copy of fmt->interpreter under entries_lock to avoid the race with kill_node() but this is not enough; the whole Node can be freed after we drop entries_lock, not only the ->interpreter string. Add dget/dput(fmt->dentry) to ensure bm_evict_inode() can't destroy/free this Node. Link: http://lkml.kernel.org/r/20170922143650.GA17227@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ben Woodard <woodard@redhat.com> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: Jim Foraker <foraker1@llnl.gov> Cc: Travis Gummels <tgummels@redhat.com> Cc: <tdhooge@llnl.gov> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/binfmt_misc.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index babfe7bd56f0..f5f8c2541790 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -138,20 +138,23 @@ static int load_misc_binary(struct linux_binprm *bprm)
retval = -ENOEXEC;
if (!enabled)
- goto ret;
+ return retval;
/* to keep locking time low, we copy the interpreter string */
read_lock(&entries_lock);
fmt = check_file(bprm);
- if (fmt)
+ if (fmt) {
+ dget(fmt->dentry);
strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
+ }
read_unlock(&entries_lock);
if (!fmt)
- goto ret;
+ return retval;
/* Need to be able to load the file after exec */
+ retval = -ENOENT;
if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
- return -ENOENT;
+ goto ret;
if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
retval = remove_arg_zero(bprm);
@@ -238,6 +241,7 @@ static int load_misc_binary(struct linux_binprm *bprm)
goto error;
ret:
+ dput(fmt->dentry);
return retval;
error:
if (fd_binary > 0)