Messages in this thread Patch in this message | | | From | ira.weiny@intel ... | Subject | [PATCH] fs/exec: Test patch for syzkaller crash | Date | Thu, 11 Aug 2022 17:09:19 -0700 |
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From: Ira Weiny <ira.weiny@intel.com>
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@chromium.org> Reported-by: syzbot+3250d9c8925ef29e975f@syzkaller.appspotmail.com Signed-off-by: Ira Weiny <ira.weiny@intel.com> --- 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
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