diff options
authorOleg Nesterov <>2016-05-23 16:24:08 -0700
committerLinus Torvalds <>2016-05-23 17:04:14 -0700
commit9eb8a659dea694b0dcbd6287f6b1fbdc523b80bc (patch)
parent725fc629ff2545b061407305ae51016c9f928fce (diff)
exec: remove the no longer needed remove_arg_zero()->free_arg_page()
remove_arg_zero() does free_arg_page() for no reason. This was needed before and only if CONFIG_MMU=y: see commit 4fc75ff4816c ("exec: fix remove_arg_zero"), install_arg_page() was called for every page != NULL in bprm->page[] array. Today install_arg_page() has already gone and free_arg_page() is nop after another commit b6a2fea39318 ("mm: variable length argument support"). CONFIG_MMU=n does free_arg_pages() in free_bprm() and thus it doesn't need remove_arg_zero()->free_arg_page() too; apart from get_arg_page() it never checks if the page in bprm->page[] was allocated or not, so the "extra" non-freed page is fine. OTOH, this free_arg_page() can add the minor pessimization, the caller is going to do copy_strings_kernel() right after remove_arg_zero() which will likely need to re-allocate the same page again. And as Hujunjie pointed out, the "offset == PAGE_SIZE" check is wrong because we are going to increment bprm->p once again before return, so CONFIG_MMU=n "leaks" the page anyway if '0' is the final byte in this page. NOTE: remove_arg_zero() assumes that argv[0] is null-terminated but this is not necessarily true. copy_strings() does "len = strnlen_user(...)", then copy_from_user(len) but another thread or debuger can overwrite the trailing '0' in between. Afaics nothing really bad can happen because we must always have the null-terminated bprm->filename copied by the 1st copy_strings_kernel(), but perhaps we should change this code to check "bprm->p < bprm->exec" anyway, and/or change copy_strings() to ensure that the last byte in string is always zero. Link: Signed-off-by: Oleg Nesterov <> Reported by: hujunjie <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
1 files changed, 0 insertions, 7 deletions
diff --git a/fs/exec.c b/fs/exec.c
index e92419fd78b3..4f079bd083af 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -243,10 +243,6 @@ static void put_arg_page(struct page *page)
-static void free_arg_page(struct linux_binprm *bprm, int i)
static void free_arg_pages(struct linux_binprm *bprm)
@@ -1499,9 +1495,6 @@ int remove_arg_zero(struct linux_binprm *bprm)
- if (offset == PAGE_SIZE)
- free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
} while (offset == PAGE_SIZE);