[PATCH] proc: pagemap: Hold mmap_sem during page walk
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From: San Mehat on 31 Mar 2010 13:30 If the mmap_sem is not held while we walk_page_range(), then it is possible for find_vma() to race with a remove_vma_list() caused by do_munmap() (or others). Unable to handle kernel paging request at virtual address 6b6b6b5b Internal error: Oops: 5 [#1] PREEMPT CPU: 0 Not tainted (2.6.32.9-27154-ge3e6e27 #1) PC is at find_vma+0x40/0x7c LR is at walk_page_range+0x70/0x230 pc : [<c00aa3ac>] lr : [<c00b298c>] psr: 20000013 sp : c6aa9eb8 ip : 6b6b6b53 fp : c6a58f60 r10: c7e1d1b8 r9 : 0001bca0 r8 : 47000000 r7 : c6aa9f80 r6 : c6aa8000 r5 : 46fbd000 r4 : 6b6b6b6b r3 : c7ca4820 r2 : 6b6b6b6b r1 : 46fbd000 r0 : c70e3e40 Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 10c5787d Table: 26574019 DAC: 00000015 [<c00aa3ac>] (find_vma+0x40/0x7c) from [<c00b298c>] (walk_page_range+0x70/0x230) [<c00b298c>] (walk_page_range+0x70/0x230) from [<c00f5d3c>] (pagemap_read+0x1a4/0x278) [<c00f5d3c>] (pagemap_read+0x1a4/0x278) from [<c00bac40>] (vfs_read+0xa8/0x150) [<c00bac40>] (vfs_read+0xa8/0x150) from [<c00bad94>] (sys_read+0x3c/0x68) [<c00bad94>] (sys_read+0x3c/0x68) from [<c0026f00>] (ret_fast_syscall+0x0/0x2c) Code: 98bd8010 e5932004 e3a00000 ea000008 (e5124010) Signed-off-by: San Mehat <san(a)google.com> Cc: Brian Swetland <swetland(a)google.com> Cc: Matt Mackall <mpm(a)selenic.com> Cc: Dave Hansen <haveblue(a)us.ibm.com> Cc: Andrew Morton <akpm(a)linux-foundation.org> Cc: Linus Torvalds <torvalds(a)linux-foundation.org> --- fs/proc/task_mmu.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 2a1bef9..3f300c1 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -726,8 +726,6 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, down_read(¤t->mm->mmap_sem); ret = get_user_pages(current, current->mm, uaddr, pagecount, 1, 0, pages, NULL); - up_read(¤t->mm->mmap_sem); - if (ret < 0) goto out_free; @@ -776,6 +774,7 @@ out_pages: page_cache_release(page); } out_free: + up_read(¤t->mm->mmap_sem); kfree(pages); out_mm: mmput(mm); -- 1.7.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |