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Unsoundness in FdSet #1572

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taylordotfish opened this issue Oct 17, 2021 · 3 comments · Fixed by #1575
Closed

Unsoundness in FdSet #1572

taylordotfish opened this issue Oct 17, 2021 · 3 comments · Fixed by #1575
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0.23.1

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@taylordotfish
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FdSet::insert, FdSet::remove, and FdSet::contains call FD_SET(), FD_CLR(), and FD_ISSET() without any bounds checking, but those underlying libc functions cause undefined behavior when provided a file descriptor outside of the range 0..FD_SETSIZE.
@taylordotfish taylordotfish changed the title Unsoundness in FdSet::insert and FdSet::remove Unsoundness in FdSet Oct 17, 2021
@asomers
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asomers commented Oct 18, 2021

Yep, it's true. Would you be willing to submit a PR to fix it?

@taylordotfish
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Sure. Is adding bounds checking an acceptable approach, despite the minor runtime cost?

@asomers
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asomers commented Oct 18, 2021

Yes. After all, select users aren't overly concerned about the runtime cost.

@asomers asomers added this to the 0.23.1 milestone Oct 18, 2021
taylordotfish added a commit to taylordotfish/nix that referenced this issue Oct 19, 2021
@taylordotfish
Fix unsoundness in FdSet methods
ccbcdb7 
Ensure file descriptors are nonnegative and less than `FD_SETSIZE`.
(Fixes nix-rust#1572.)
@taylordotfish taylordotfish mentioned this issue Oct 19, 2021
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taylordotfish added a commit to taylordotfish/nix that referenced this issue Oct 21, 2021
@taylordotfish
Fix unsoundness in FdSet methods
88671ed 
Ensure file descriptors are nonnegative and less than `FD_SETSIZE`.
(Fixes nix-rust#1572.)
bors bot added a commit that referenced this issue Oct 22, 2021
@bors @taylordotfish
Merge #1575
3429165 
1575: Fix unsoundness in FdSet methods r=asomers a=taylordotfish

Ensure file descriptors are nonnegative and less than `FD_SETSIZE`. (Fixes #1572.)

Co-authored-by: taylor.fish <contact@taylor.fish>
@bors bors bot closed this as completed in dc80b4c Oct 22, 2021
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Fix unsoundness in FdSet methods taylordotfish/nix
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@asomers @taylordotfish