Re: linux-next: Tree for Nov 7
From: Michal Hocko <mhocko@kernel.org>
Date: 2017-11-13 15:16:51
Also in:
linux-arm-kernel, linux-mips, linux-next, linux-sh, lkml, sparclinux
Subsystem:
alpha port, generic include/asm header files, memory management, memory mapping, memory mapping - madvise (memory advice), mips, parisc architecture, tensilica xtensa port (xtensa), the rest · Maintainers:
Richard Henderson, Matt Turner, Magnus Lindholm, Arnd Bergmann, Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, David Hildenbrand, Thomas Bogendoerfer, "James E.J. Bottomley", Helge Deller, Chris Zankel, Max Filippov, Linus Torvalds
On Mon 13-11-17 13:00:57, Michal Hocko wrote: [...]
Yes, I have mentioned that in the previous email but the amount of code would be even larger. Basically every arch which reimplements arch_get_unmapped_area would have to special case new MAP_FIXED flag to do vma lookup.
It turned out that this might be much more easier than I thought after all. It seems we can really handle that in the common code. This would mean that we are exposing a new functionality to the userspace though. Myabe this would be useful on its own though. Just a quick draft (not even compile tested) whether this makes sense in general. I would be worried about unexpected behavior when somebody set other bit without a good reason and we might fail with ENOMEM for such a call now. Elf loader would then use MAP_FIXED_SAFE rather than MAP_FIXED. ---
diff --git a/arch/alpha/include/uapi/asm/mman.h b/arch/alpha/include/uapi/asm/mman.h
index 3b26cc62dadb..d021c21f9b01 100644
--- a/arch/alpha/include/uapi/asm/mman.h
+++ b/arch/alpha/include/uapi/asm/mman.h@@ -31,6 +31,9 @@ #define MAP_STACK 0x80000 /* give out an address that is best suited for process/thread stacks */ #define MAP_HUGETLB 0x100000 /* create a huge page mapping */ +#define MAP_KEEP_MAPPING 0x2000000 +#define MAP_FIXED_SAFE MAP_FIXED|MAP_KEEP_MAPPING /* enforce MAP_FIXED without clobbering an existing mapping */ + #define MS_ASYNC 1 /* sync memory asynchronously */ #define MS_SYNC 2 /* synchronous memory sync */ #define MS_INVALIDATE 4 /* invalidate the caches */
diff --git a/arch/mips/include/uapi/asm/mman.h b/arch/mips/include/uapi/asm/mman.h
index da3216007fe0..51e3885fbfc1 100644
--- a/arch/mips/include/uapi/asm/mman.h
+++ b/arch/mips/include/uapi/asm/mman.h@@ -49,6 +49,9 @@ #define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */ #define MAP_HUGETLB 0x80000 /* create a huge page mapping */ +#define MAP_KEEP_MAPPING 0x2000000 +#define MAP_FIXED_SAFE MAP_FIXED|MAP_KEEP_MAPPING /* enforce MAP_FIXED without clobbering an existing mapping */ + /* * Flags for msync */
diff --git a/arch/parisc/include/uapi/asm/mman.h b/arch/parisc/include/uapi/asm/mman.h
index cc9ba1d34779..5a4381484fc5 100644
--- a/arch/parisc/include/uapi/asm/mman.h
+++ b/arch/parisc/include/uapi/asm/mman.h@@ -25,6 +25,9 @@ #define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */ #define MAP_HUGETLB 0x80000 /* create a huge page mapping */ +#define MAP_KEEP_MAPPING 0x2000000 +#define MAP_FIXED_SAFE MAP_FIXED|MAP_KEEP_MAPPING /* enforce MAP_FIXED without clobbering an existing mapping */ + #define MS_SYNC 1 /* synchronous memory sync */ #define MS_ASYNC 2 /* sync memory asynchronously */ #define MS_INVALIDATE 4 /* invalidate the caches */
diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h
index b15b278aa314..5df8a81524da 100644
--- a/arch/xtensa/include/uapi/asm/mman.h
+++ b/arch/xtensa/include/uapi/asm/mman.h@@ -62,6 +62,9 @@ # define MAP_UNINITIALIZED 0x0 /* Don't support this flag */ #endif +#define MAP_KEEP_MAPPING 0x2000000 +#define MAP_FIXED_SAFE MAP_FIXED|MAP_KEEP_MAPPING /* enforce MAP_FIXED without clobbering an existing mapping */ + /* * Flags for msync */
diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
index 203268f9231e..22442846f5c8 100644
--- a/include/uapi/asm-generic/mman-common.h
+++ b/include/uapi/asm-generic/mman-common.h@@ -25,6 +25,9 @@ # define MAP_UNINITIALIZED 0x0 /* Don't support this flag */ #endif +#define MAP_KEEP_MAPPING 0x2000000 +#define MAP_FIXED_SAFE MAP_FIXED|MAP_KEEP_MAPPING /* enforce MAP_FIXED without clobbering an existing mapping */ + /* * Flags for mlock */
diff --git a/mm/mmap.c b/mm/mmap.c
index 680506faceae..e53b6b15a8d9 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c@@ -1365,6 +1365,13 @@ unsigned long do_mmap(struct file *file, unsigned long addr, if (offset_in_page(addr)) return addr; + if ((flags & MAP_FIXED_SAFE) == MAP_FIXED_SAFE) { + struct vm_area_struct *vma = find_vma(mm, addr); + + if (vma && vma->vm_start <= addr) + return -ENOMEM; + } + if (prot == PROT_EXEC) { pkey = execute_only_pkey(mm); if (pkey < 0)
--
Michal Hocko
SUSE Labs