From c3dd50da0f4d00fffe8ea5e211c2c189fe6ad4fb Mon Sep 17 00:00:00 2001 From: Akihiko Odaki Date: Wed, 2 Aug 2023 16:17:47 +0900 Subject: [PATCH] linux-user: Unset MAP_FIXED_NOREPLACE for host Passing MAP_FIXED_NOREPLACE to host will fail for reserved_va because the address space is reserved with mmap. Replace it with MAP_FIXED in that case. Signed-off-by: Akihiko Odaki Message-Id: <20230802071754.14876-2-akihiko.odaki@daynix.com> [rth: Expand inline commentary.] Reviewed-by: Richard Henderson Signed-off-by: Richard Henderson --- linux-user/mmap.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index a5dfb56545..a11c630a7b 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -603,11 +603,26 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot, goto fail; } - /* Validate that the chosen range is empty. */ - if ((flags & MAP_FIXED_NOREPLACE) - && !page_check_range_empty(start, last)) { - errno = EEXIST; - goto fail; + if (flags & MAP_FIXED_NOREPLACE) { + /* Validate that the chosen range is empty. */ + if (!page_check_range_empty(start, last)) { + errno = EEXIST; + goto fail; + } + + /* + * With reserved_va, the entire address space is mmaped in the + * host to ensure it isn't accidentally used for something else. + * We have just checked that the guest address is not mapped + * within the guest, but need to replace the host reservation. + * + * Without reserved_va, despite the guest address check above, + * keep MAP_FIXED_NOREPLACE so that the guest does not overwrite + * any host address mappings. + */ + if (reserved_va) { + flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED; + } } /*