From: Ira Weiny <ira.weiny@xxxxxxxxx> Kees reported that it looked like the kmap_local_page() conversion in fs/exec.c was causing a crash with the syzkaller.[1] At first glance it appeared this was due to the lack of pagefaults not being disabled as was done by kmap_atomic(). Unfortunately, after deeper investigation we don't see how this is a problem. The crash does not appear to be happening in the memcpy_to_page() call.[2] For testing, add back pagefault disable in copy_string_kernel() to see if it makes syzkaller happy. If so more investigation will need to be done to understand exactly what is happening. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c6e8e36c6ae4b11bed5643317afb66b6c3cadba8 [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/fs/exec.c?id=40d43a7507e1547dd45cb02af2e40d897c591870#n616 Cc: Kees Cook <keescook@xxxxxxxxxxxx> Reported-by: syzbot+3250d9c8925ef29e975f@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> --- fs/exec.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/exec.c b/fs/exec.c index b51dd14e7388..e076b228123a 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -640,7 +640,9 @@ int copy_string_kernel(const char *arg, struct linux_binprm *bprm) if (!page) return -E2BIG; flush_arg_page(bprm, pos & PAGE_MASK, page); + pagefault_disable(); memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy); + pagefault_enable(); put_arg_page(page); } -- 2.35.3
