SUNRPC: Prevent kernel stack corruption on long values of flush
The buffer size in read_flush() is too small for the longest possible values for it. This can lead to a kernel stack corruption: [ 43.047329] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff833e64b4 [ 43.047329] [ 43.049030] Pid: 6015, comm: trinity-child18 Tainted: G W 3.5.0-rc7-next-20120716-sasha #221 [ 43.050038] Call Trace: [ 43.050435] [<ffffffff836c60c2>] panic+0xcd/0x1f4 [ 43.050931] [<ffffffff833e64b4>] ? read_flush.isra.7+0xe4/0x100 [ 43.051602] [<ffffffff810e94e6>] __stack_chk_fail+0x16/0x20 [ 43.052206] [<ffffffff833e64b4>] read_flush.isra.7+0xe4/0x100 [ 43.052951] [<ffffffff833e6500>] ? read_flush_pipefs+0x30/0x30 [ 43.053594] [<ffffffff833e652c>] read_flush_procfs+0x2c/0x30 [ 43.053596] [<ffffffff812b9a8c>] proc_reg_read+0x9c/0xd0 [ 43.053596] [<ffffffff812b99f0>] ? proc_reg_write+0xd0/0xd0 [ 43.053596] [<ffffffff81250d5b>] do_loop_readv_writev+0x4b/0x90 [ 43.053596] [<ffffffff81250fd6>] do_readv_writev+0xf6/0x1d0 [ 43.053596] [<ffffffff812510ee>] vfs_readv+0x3e/0x60 [ 43.053596] [<ffffffff812511b8>] sys_readv+0x48/0xb0 [ 43.053596] [<ffffffff8378167d>] system_call_fastpath+0x1a/0x1f Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Cc: stable@kernel.org Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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@ -1409,11 +1409,11 @@ static ssize_t read_flush(struct file *file, char __user *buf,
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size_t count, loff_t *ppos,
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struct cache_detail *cd)
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{
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char tbuf[20];
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char tbuf[22];
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unsigned long p = *ppos;
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size_t len;
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sprintf(tbuf, "%lu\n", convert_to_wallclock(cd->flush_time));
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snprintf(tbuf, sizeof(tbuf), "%lu\n", convert_to_wallclock(cd->flush_time));
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len = strlen(tbuf);
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if (p >= len)
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return 0;
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