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authorKees Cook <keescook@chromium.org>2012-12-18 04:03:20 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-18 05:15:23 +0400
commitd740269867021faf4ce38a449353d2b986c34a67 (patch)
treee0476e1be1dfb6e852adbaa8fb72ecea87bdb088 /fs/binfmt_script.c
parent8d238027b87e654be552eabdf492042a34c5c300 (diff)
downloadlinux-d740269867021faf4ce38a449353d2b986c34a67.tar.xz
exec: use -ELOOP for max recursion depth
To avoid an explosion of request_module calls on a chain of abusive scripts, fail maximum recursion with -ELOOP instead of -ENOEXEC. As soon as maximum recursion depth is hit, the error will fail all the way back up the chain, aborting immediately. This also has the side-effect of stopping the user's shell from attempting to reexecute the top-level file as a shell script. As seen in the dash source: if (cmd != path_bshell && errno == ENOEXEC) { *argv-- = cmd; *argv = cmd = path_bshell; goto repeat; } The above logic was designed for running scripts automatically that lacked the "#!" header, not to re-try failed recursion. On a legitimate -ENOEXEC, things continue to behave as the shell expects. Additionally, when tracking recursion, the binfmt handlers should not be involved. The recursion being tracked is the depth of calls through search_binary_handler(), so that function should be exclusively responsible for tracking the depth. Signed-off-by: Kees Cook <keescook@chromium.org> Cc: halfdog <me@halfdog.net> Cc: P J P <ppandit@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/binfmt_script.c')
-rw-r--r--fs/binfmt_script.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c
index 8c954997e7f7..1610a91637e5 100644
--- a/fs/binfmt_script.c
+++ b/fs/binfmt_script.c
@@ -22,15 +22,13 @@ static int load_script(struct linux_binprm *bprm)
char interp[BINPRM_BUF_SIZE];
int retval;
- if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!') ||
- (bprm->recursion_depth > BINPRM_MAX_RECURSION))
+ if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
return -ENOEXEC;
/*
* This section does the #! interpretation.
* Sorta complicated, but hopefully it will work. -TYT
*/
- bprm->recursion_depth++;
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;