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author | Peter Zijlstra <peterz@infradead.org> | 2023-10-18 14:56:54 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-10-25 12:54:25 +0300 |
commit | 487a8e24643a0effb2ba19cad3227fc75dc3c4b7 (patch) | |
tree | c1049d0ba2a813c847e6eb7ccfdb43805daa97f1 /include/media/rc-map.h | |
parent | 550c70f72a1b00190111c7247319eb94dc5d3dab (diff) | |
download | linux-487a8e24643a0effb2ba19cad3227fc75dc3c4b7.tar.xz |
perf: Disallow mis-matched inherited group reads
commit 32671e3799ca2e4590773fd0e63aaa4229e50c06 upstream.
Because group consistency is non-atomic between parent (filedesc) and children
(inherited) events, it is possible for PERF_FORMAT_GROUP read() to try and sum
non-matching counter groups -- with non-sensical results.
Add group_generation to distinguish the case where a parent group removes and
adds an event and thus has the same number, but a different configuration of
events as inherited groups.
This became a problem when commit fa8c269353d5 ("perf/core: Invert
perf_read_group() loops") flipped the order of child_list and sibling_list.
Previously it would iterate the group (sibling_list) first, and for each
sibling traverse the child_list. In this order, only the group composition of
the parent is relevant. By flipping the order the group composition of the
child (inherited) events becomes an issue and the mis-match in group
composition becomes evident.
That said; even prior to this commit, while reading of a group that is not
equally inherited was not broken, it still made no sense.
(Ab)use ECHILD as error return to indicate issues with child process group
composition.
Fixes: fa8c269353d5 ("perf/core: Invert perf_read_group() loops")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231018115654.GK33217@noisy.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/media/rc-map.h')
0 files changed, 0 insertions, 0 deletions