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arm64: mmap: Ensure file offset is treated as unsigned

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commit f08cae2f28db24d95be5204046b60618d8de4ddc upstream.

The file offset argument to the arm64 sys_mmap() implementation is
scaled from bytes to pages by shifting right by PAGE_SHIFT.
Unfortunately, the offset is passed in as a signed 'off_t' type and
therefore large offsets (i.e. with the top bit set) are incorrectly
sign-extended by the shift. This has been observed to cause false mmap()
failures when mapping GPU doorbells on an arm64 server part.

Change the type of the file offset argument to sys_mmap() from 'off_t'
to 'unsigned long' so that the shifting scales the value as expected.

Cc: <stable@vger.kernel.org>
Signed-off-by: Boyang Zhou <zhouby_cn@126.com>
[will: rewrote commit message]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Boyang Zhou 2019-04-29 15:27:19 +01:00 • committed by Greg Kroah-Hartman
parent 592127e9c1
commit 222abad906
1 changed files with 1 additions and 1 deletions

2
arch/arm64/kernel/sys.c
View file

@ -31,7 +31,7 @@
SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags,
unsigned long, fd, off_t, off)
unsigned long, fd, unsigned long, off)
{
if (offset_in_page(off) != 0)
return -EINVAL;