Florian Weimer points out an issue with including linux/posix_types.h from arbitrary other headers: if an application has defined a macro named 'fds_bits', it may stop compiling after a change in the kernel headers. Since fds_bits is a non-reserved identifier in C, that is considered a bug in the kernel headers. The structure definition does not really seem to be helpful here, as the kernel no longer provides macros to manipulate it. The only user of the structure that we could find was in libsanitize. This usage is actually broken, as discussed in the email thread, but this means we cannot just remove the definition from the exported headers, but we can use the __kernel_* namespace for it, to avoid the namespace conflict. The kernel itself just uses bit operations on the typedef without accessing the field by name. This change should also help with the many other kernel headers that include linux/posix_types.h directly or through linux/types.h. Similarly, the definition of __kernel_fsid_t uses a structure with field identifier 'val' that may have the same problem. Again, user space should not rely on the specific field name but instead treat an fsid_t as an opaque identifier. I'm using an #ifdef __KERNEL__ guard here to save us from having to change all kernel code accessing the field. Glibc has changed this from 'val' to '__val' back in 1996/97 when they moved away from using the kernel types directly, it it is likely that nothing uses __kernel_fsid_t any more. MIPS still has another copy of __kernel_fsid_t, but that is in the process of being removed as well. Link: https://lore.kernel.org/lkml/87a7hvded7.fsf@xxxxxxxxxxxxxxxxx/ Link: https://lore.kernel.org/lkml/20190314173900.25454-1-paul.burton@xxxxxxxx/ Cc: Florian Weimer <fw@xxxxxxxxxxxxx> Cc: Paul Burton <pburton@xxxxxxxxxxxx> Fixes: a623a7a1a567 ("y2038: fix socket.h header inclusion") Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> --- There was another bug report for the same change just now, so I wouldn't apply this patch yet before we have fully understood the other issue. Sending this for review now since the two problems are most likely independent. --- include/uapi/asm-generic/posix_types.h | 4 ++++ include/uapi/linux/posix_types.h | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/include/uapi/asm-generic/posix_types.h b/include/uapi/asm-generic/posix_types.h index f0733a26ebfc..2a8c68ac88ca 100644 --- a/include/uapi/asm-generic/posix_types.h +++ b/include/uapi/asm-generic/posix_types.h @@ -77,7 +77,11 @@ typedef __kernel_long_t __kernel_ptrdiff_t; #ifndef __kernel_fsid_t typedef struct { +#ifdef __KERNEL__ int val[2]; +#else + int __kernel_val[2]; +#endif } __kernel_fsid_t; #endif diff --git a/include/uapi/linux/posix_types.h b/include/uapi/linux/posix_types.h index 9a7a740b35a2..a5a5cfc38bbf 100644 --- a/include/uapi/linux/posix_types.h +++ b/include/uapi/linux/posix_types.h @@ -23,7 +23,7 @@ #define __FD_SETSIZE 1024 typedef struct { - unsigned long fds_bits[__FD_SETSIZE / (8 * sizeof(long))]; + unsigned long __kernel_fds_bits[__FD_SETSIZE / (8 * sizeof(long))]; } __kernel_fd_set; /* Type of a signal handler. */ -- 2.20.0
