diff options
Diffstat (limited to 'freed-ora/current/f12/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch')
| -rw-r--r-- | freed-ora/current/f12/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/freed-ora/current/f12/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch b/freed-ora/current/f12/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch new file mode 100644 index 000000000..095a9336d --- /dev/null +++ b/freed-ora/current/f12/mm-fix-up-some-user-visible-effects-of-the-stack-guard-page.patch @@ -0,0 +1,85 @@ +From: Linus Torvalds <torvalds@linux-foundation.org> +Date: Sun, 15 Aug 2010 18:35:52 +0000 (-0700) +Subject: mm: fix up some user-visible effects of the stack guard page +X-Git-Tag: v2.6.36-rc1~5 +X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=d7824370e26325c881b665350ce64fb0a4fde24a + +mm: fix up some user-visible effects of the stack guard page + +This commit makes the stack guard page somewhat less visible to user +space. It does this by: + + - not showing the guard page in /proc/<pid>/maps + + It looks like lvm-tools will actually read /proc/self/maps to figure + out where all its mappings are, and effectively do a specialized + "mlockall()" in user space. By not showing the guard page as part of + the mapping (by just adding PAGE_SIZE to the start for grows-up + pages), lvm-tools ends up not being aware of it. + + - by also teaching the _real_ mlock() functionality not to try to lock + the guard page. + + That would just expand the mapping down to create a new guard page, + so there really is no point in trying to lock it in place. + +It would perhaps be nice to show the guard page specially in +/proc/<pid>/maps (or at least mark grow-down segments some way), but +let's not open ourselves up to more breakage by user space from programs +that depends on the exact deails of the 'maps' file. + +Special thanks to Henrique de Moraes Holschuh for diving into lvm-tools +source code to see what was going on with the whole new warning. + +Reported-and-tested-by: François Valenduc <francois.valenduc@tvcablenet.be +Reported-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> +Cc: stable@kernel.org +Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> +--- + +diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c +index aea1d3f..439fc1f 100644 +--- a/fs/proc/task_mmu.c ++++ b/fs/proc/task_mmu.c +@@ -210,6 +210,7 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) + int flags = vma->vm_flags; + unsigned long ino = 0; + unsigned long long pgoff = 0; ++ unsigned long start; + dev_t dev = 0; + int len; + +@@ -220,8 +221,13 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) + pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT; + } + ++ /* We don't show the stack guard page in /proc/maps */ ++ start = vma->vm_start; ++ if (vma->vm_flags & VM_GROWSDOWN) ++ start += PAGE_SIZE; ++ + seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n", +- vma->vm_start, ++ start, + vma->vm_end, + flags & VM_READ ? 'r' : '-', + flags & VM_WRITE ? 'w' : '-', +diff --git a/mm/mlock.c b/mm/mlock.c +index 3f82720..49e5e4c 100644 +--- a/mm/mlock.c ++++ b/mm/mlock.c +@@ -167,6 +167,14 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma, + if (vma->vm_flags & VM_WRITE) + gup_flags |= FOLL_WRITE; + ++ /* We don't try to access the guard page of a stack vma */ ++ if (vma->vm_flags & VM_GROWSDOWN) { ++ if (start == vma->vm_start) { ++ start += PAGE_SIZE; ++ nr_pages--; ++ } ++ } ++ + while (nr_pages > 0) { + int i; + |
