BACKPORT: aio: mark AIO pseudo-fs noexec
This ensures that do_mmap() won't implicitly make AIO memory mappings executable if the READ_IMPLIES_EXEC personality flag is set. Such behavior is problematic because the security_mmap_file LSM hook doesn't catch this case, potentially permitting an attacker to bypass a W^X policy enforced by SELinux. I have tested the patch on my machine. To test the behavior, compile and run this: #define _GNU_SOURCE #include <unistd.h> #include <sys/personality.h> #include <linux/aio_abi.h> #include <err.h> #include <stdlib.h> #include <stdio.h> #include <sys/syscall.h> int main(void) { personality(READ_IMPLIES_EXEC); aio_context_t ctx = 0; if (syscall(__NR_io_setup, 1, &ctx)) err(1, "io_setup"); char cmd[1000]; sprintf(cmd, "cat /proc/%d/maps | grep -F '/[aio]'", (int)getpid()); system(cmd); return 0; } In the output, "rw-s" is good, "rwxs" is bad. Signed-off-by: Jann Horn <jann@thejh.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> (cherry picked from commit 22f6b4d34fcf039c63a94e7670e0da24f8575a5a) Bug: 31711619 Change-Id: I9f2872703bef240d6b82320c744529459bb076dc CVE-2016-10044 Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
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fs/aio.c
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fs/aio.c
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@ -35,6 +35,7 @@
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#include <linux/eventfd.h>
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#include <linux/blkdev.h>
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#include <linux/compat.h>
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#include <linux/personality.h>
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#include <asm/kmap_types.h>
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#include <asm/uaccess.h>
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@ -111,6 +112,9 @@ static int aio_setup_ring(struct kioctx *ctx)
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unsigned long size;
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int nr_pages;
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if (current->personality & READ_IMPLIES_EXEC)
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return -EPERM;
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/* Compensate for the ring buffer's head/tail overlap entry */
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nr_events += 2; /* 1 is required, 2 for good luck */
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