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PROT_WRITE isn't need for a mapping of a file with MAP_SHARED

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A file destriptor is opened for read-only and mmap with PROT_WRITE fails.
We don't need PROT_WRITE for this case, because a file contains up to date
data.

lr-x------ 1 root root 64 Dec  1 19:10 20 -> /usr/lib64/gconv/gconv-modules.cache
pos:    0
flags:    0100000
41155 mmap(0x7f2c3d6cf000, 28672, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, 20, 0 <unfinished ...>
41155 <... mmap resumed> )              = -1 EACCES (Permission denied)

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
This commit is contained in:
Andrey Vagin
2011-12-02 15:33:00 +04:00
committed by Cyrill Gorcunov
parent fa28f40aaa
commit cbb6b2da3d
1 changed files with 9 additions and 1 deletions
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10
restorer.c
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@@ -216,6 +216,8 @@ self_len_end:
*/ */
sys_lseek(args->fd_core, GET_FILE_OFF_AFTER(struct core_entry), SEEK_SET); sys_lseek(args->fd_core, GET_FILE_OFF_AFTER(struct core_entry), SEEK_SET);
while (1) { while (1) {
int prot;
ret = sys_read(args->fd_core, vma_entry, sizeof(*vma_entry)); ret = sys_read(args->fd_core, vma_entry, sizeof(*vma_entry));
if (!ret) if (!ret)
break; break;
@@ -242,6 +244,12 @@ self_len_end:
vma_entry->flags &= ~MAP_ANONYMOUS; vma_entry->flags &= ~MAP_ANONYMOUS;
} }
prot = vma_entry->prot;
/* A mapping of file with MAP_SHARED is up to date */
if (vma_entry->fd == -1 || !(vma_entry->flags & MAP_SHARED))
prot |= PROT_WRITE;
/* /*
* Should map memory here. Note we map them as * Should map memory here. Note we map them as
* writable since we're going to restore page * writable since we're going to restore page
@@ -249,7 +257,7 @@ self_len_end:
*/ */
va = sys_mmap((void *)vma_entry->start, va = sys_mmap((void *)vma_entry->start,
vma_entry_len(vma_entry), vma_entry_len(vma_entry),
vma_entry->prot | PROT_WRITE, prot,
vma_entry->flags | MAP_FIXED, vma_entry->flags | MAP_FIXED,
vma_entry->fd, vma_entry->fd,
vma_entry->pgoff); vma_entry->pgoff);