From: Jeff Layton Date: Tue, 21 Jul 2009 23:42:03 +0000 (-0400) Subject: cifs: fix sb->s_maxbytes so that it casts properly to a signed value X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=03aa3a49ad3592a9e4e1ab19c6da3e852288caf1;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git cifs: fix sb->s_maxbytes so that it casts properly to a signed value This off-by-one bug causes sendfile() to not work properly. When a task calls sendfile() on a file on a CIFS filesystem, the syscall returns -1 and sets errno to EOVERFLOW. do_sendfile uses s_maxbytes to verify the returned offset of the file. The problem there is that this value is cast to a signed value (loff_t). When this is done on the s_maxbytes value that cifs uses, it becomes negative and the comparisons against it fail. Even though s_maxbytes is an unsigned value, it seems that it's not OK to set it in such a way that it'll end up negative when it's cast to a signed value. These casts happen in other codepaths besides sendfile too, but the VFS is a little hard to follow in this area and I can't be sure if there are other bugs that this will fix. It's not clear to me why s_maxbytes isn't just declared as loff_t in the first place, but either way we still need to fix these values to make sendfile work properly. This is also an opportunity to replace the magic bit-shift values here with the standard #defines for this. This fixes the reproducer program I have that does a sendfile and will probably also fix the situation where apache is serving from a CIFS share. Acked-by: Johannes Weiner Signed-off-by: Jeff Layton Signed-off-by: Steve French --- diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 9bb5c8750736..fc44d316d0bb 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -2452,10 +2452,10 @@ try_mount_again: tcon->local_lease = volume_info->local_lease; } if (pSesInfo) { - if (pSesInfo->capabilities & CAP_LARGE_FILES) { - sb->s_maxbytes = (u64) 1 << 63; - } else - sb->s_maxbytes = (u64) 1 << 31; /* 2 GB */ + if (pSesInfo->capabilities & CAP_LARGE_FILES) + sb->s_maxbytes = MAX_LFS_FILESIZE; + else + sb->s_maxbytes = MAX_NON_LFS; } /* BB FIXME fix time_gran to be larger for LANMAN sessions */