ssh/sftp: fix resume corruption by avoiding O_APPEND with rresume #18952
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Opening the remote file with O_APPEND while attempting to resume causes all writes to be forced to EOF on servers/implementations where O_APPEND semantics override a prior seek(). As a result, sftp_seek64() is ignored and the resumed data is appended, duplicating/corrupting the file. Fix by: - Using O_WRONLY (without O_APPEND) when resume_from > 0. - Skipping the seek entirely if remote_append mode is requested.
Opening the remote file with O_APPEND while attempting to resume causes all writes to be forced to EOF on servers/implementations where O_APPEND semantics override a prior seek(). As a result, sftp_seek64() is ignored and the resumed data is appended, duplicating/corrupting the file. Fix by: - Using O_WRONLY (without O_APPEND) when resume_from > 0. - Skipping the seek entirely if remote_append mode is requested.
bagder
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Oct 9, 2025
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Opening the remote file with O_APPEND while attempting to resume causes all writes to be forced to EOF on servers/implementations where O_APPEND semantics override a prior seek(). As a result, sftp_seek64() is ignored and the resumed data is appended, duplicating/corrupting the file. Fix by: - Using O_WRONLY (without O_APPEND) when resume_from > 0. - Skipping the seek entirely if remote_append mode is requested. Closes #18952
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Opening the remote file with O_APPEND while attempting to resume causes
all writes to be forced to EOF on servers/implementations where O_APPEND
semantics override a prior seek(). As a result, sftp_seek64() is ignored
and the resumed data is appended, duplicating/corrupting the file.
Fix by: