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Message-ID: <bb2991f8-323a-c835-0b04-ff8d565df0fa@infradead.org>
Date: Sun, 14 Apr 2019 08:24:53 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Alexey Dobriyan <adobriyan@...il.com>, akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: fix map_files test on F29
On 4/14/19 5:36 AM, Alexey Dobriyan wrote:
> F29 bans mapping first 64KB even for root making test fail.
so there is an F29-only patch that prevents that?
something that is not in mainline?
thanks.
> Iterate from address 0 until mmap() works.
>
> Gentoo (root):
>
> openat(AT_FDCWD, "/dev/zero", O_RDONLY) = 3
> mmap(NULL, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0
>
> Gentoo (non-root):
>
> openat(AT_FDCWD, "/dev/zero", O_RDONLY) = 3
> mmap(NULL, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EPERM (Operation not permitted)
> mmap(0x1000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x1000
>
> F29 (root):
>
> openat(AT_FDCWD, "/dev/zero", O_RDONLY) = 3
> mmap(NULL, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x1000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x2000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x3000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x4000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x5000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x6000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x7000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x8000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x9000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0xa000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0xb000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0xc000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0xd000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0xe000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0xf000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = -1 EACCES (Permission denied)
> mmap(0x10000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x10000
>
> Now all proc tests succeed on F29 if run as root, at last!
>
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> ---
>
> tools/testing/selftests/proc/proc-self-map-files-002.c | 20 ++++++++---------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> --- a/tools/testing/selftests/proc/proc-self-map-files-002.c
> +++ b/tools/testing/selftests/proc/proc-self-map-files-002.c
> @@ -46,12 +46,9 @@ static void fail(const char *fmt, unsigned long a, unsigned long b)
>
> int main(void)
> {
> - const unsigned int PAGE_SIZE = sysconf(_SC_PAGESIZE);
> -#ifdef __arm__
> - unsigned long va = 2 * PAGE_SIZE;
> -#else
> - unsigned long va = 0;
> -#endif
> + const int PAGE_SIZE = sysconf(_SC_PAGESIZE);
> + const unsigned long va_max = 1UL << 32;
> + unsigned long va;
> void *p;
> int fd;
> unsigned long a, b;
> @@ -60,10 +57,13 @@ int main(void)
> if (fd == -1)
> return 1;
>
> - p = mmap((void *)va, PAGE_SIZE, PROT_NONE, MAP_PRIVATE|MAP_FILE|MAP_FIXED, fd, 0);
> - if (p == MAP_FAILED) {
> - if (errno == EPERM)
> - return 4;
> + for (va = 0; va < va_max; va += PAGE_SIZE) {
> + p = mmap((void *)va, PAGE_SIZE, PROT_NONE, MAP_PRIVATE|MAP_FILE|MAP_FIXED, fd, 0);
> + if (p == (void *)va)
> + break;
> + }
> + if (va == va_max) {
> + fprintf(stderr, "error: mmap doesn't like you\n");
> return 1;
> }
>
>
--
~Randy
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