[linux] fix: memory-mapped file, stat: No such file or directory #329
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In old linux kernel (e.g. linux-2.6) which does not have this feature: Commit
6b4e306aa3dc ("ns: proc files for namespace naming policy."), means this path
"/proc/self/ns" is not existed. Since lsof-4.96.0 with Commit dbad150 ("
[linux] obtain correct information of memory-mapped file."), compare_mntns()
would misunderstand it is in a different mount namespace if "/proc/self/ns" is
not existed, returns -1, go through map_files lookup, and finally lead to lsof
gets failed with error message "stat: No such file or directory".
If "/proc/self/ns" or its underlying path is not existed, compare_mntns()
returns 0 instead of -1, in order to go through stat_directly as old days.
Signed-off-by: Jones Syue <[email protected]>
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Nice observation! Regarding the code change, maybe we could add some comments on the logic behind comparison: when it is regarded as different, and how it works in different kernel versions. |
Add comments: Compare the inode number of mount namespace, to see if target process is in a different mount namespace from lsof process: return 0 (false) means mount namespace is the same, and return 1 (true) means mount namespace is different. Note that legacy linux kernel (e.g. linux-2.6) might not have this mount namespace path, so makes this case return 0 (false) and acts as old days. Signed-off-by: Jones Syue <[email protected]>
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Hello @jiegec Thank you for kind feedback! Add comments and hope im doing this in the correct way :) |
|
Thank you @jiegec and your time :) |
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Describe the bug
Since lsof-4.96.0, run lsof with old linux kernel (e.g. linux-2.6),
lsof would print error message "stat: No such file or directory"
when visiting memory-mapped files; but /bin/stat could visit it without issue.
lsof-4.95.0 and earlier does not have this issue.
In old linux kernel (e.g. linux-2.6) which does not have this feature: Commit
6b4e306aa3dc ("ns: proc files for namespace naming policy."), means this path
"/proc/self/ns" is not existed. Since lsof-4.96.0 with Commit dbad150 ("
[linux] obtain correct information of memory-mapped file."), compare_mntns()
would misunderstand it is in a different mount namespace if "/proc/self/ns" is
not existed, returns -1, go through map_files lookup, and finally lead to lsof
gets failed with error message "stat: No such file or directory".
If "/proc/self/ns" or its underlying path is not existed, compare_mntns()
returns 0 instead of -1, in order to go through stat_directly as old days.
To Reproduce
Steps to reproduce the behavior:
Expected behavior
Should not print 'stat: No such file or directory'.
Program output
Environment (please complete the following information):